Experimental Investigation of Electrical Conductivity and Permittivity of SC-TiO 2 -EG Nanofluids.

PubMed

Fal, Jacek; Barylyak, Adriana; Besaha, Khrystyna; Bobitski, Yaroslav V; Cholewa, Marian; Zawlik, Izabela; Szmuc, Kamil; Cebulski, Józef; Żyła, Gaweł

2016-12-01

The paper presents experimental studies of dielectric properties of nanofluids based on ethylene glycol and SC-TiO2 nanoparticles with average size of 15-40 nm with various mass concentrations. The dielectric permittivity both real part and imaginary part as a function of temperature and frequency were measured. Also, dependence ac conductivity on frequency, temperature, and mass concentration were investigated. Based on the curves of ac conductivity, dc conductivity was calculated, and 400 % enhancement in dc conductivity was exposed.

Experimental Investigation of Electrical Conductivity and Permittivity of SC-TiO 2 -EG Nanofluids

NASA Astrophysics Data System (ADS)

Fal, Jacek; Barylyak, Adriana; Besaha, Khrystyna; Bobitski, Yaroslav V.; Cholewa, Marian; Zawlik, Izabela; Szmuc, Kamil; Cebulski, Józef; żyła, Gaweł

2016-08-01

The paper presents experimental studies of dielectric properties of nanofluids based on ethylene glycol and SC-TiO2 nanoparticles with average size of 15-40 nm with various mass concentrations. The dielectric permittivity both real part and imaginary part as a function of temperature and frequency were measured. Also, dependence ac conductivity on frequency, temperature, and mass concentration were investigated. Based on the curves of ac conductivity, dc conductivity was calculated, and 400 % enhancement in dc conductivity was exposed.

A DTI-based model for TMS using the independent impedance method with frequency-dependent tissue parameters

NASA Astrophysics Data System (ADS)

De Geeter, N.; Crevecoeur, G.; Dupré, L.; Van Hecke, W.; Leemans, A.

2012-04-01

Accurate simulations on detailed realistic head models are necessary to gain a better understanding of the response to transcranial magnetic stimulation (TMS). Hitherto, head models with simplified geometries and constant isotropic material properties are often used, whereas some biological tissues have anisotropic characteristics which vary naturally with frequency. Moreover, most computational methods do not take the tissue permittivity into account. Therefore, we calculate the electromagnetic behaviour due to TMS in a head model with realistic geometry and where realistic dispersive anisotropic tissue properties are incorporated, based on T1-weighted and diffusion-weighted magnetic resonance images. This paper studies the impact of tissue anisotropy, permittivity and frequency dependence, using the anisotropic independent impedance method. The results show that anisotropy yields differences up to 32% and 19% of the maximum induced currents and electric field, respectively. Neglecting the permittivity values leads to a decrease of about 72% and 24% of the maximum currents and field, respectively. Implementing the dispersive effects of biological tissues results in a difference of 6% of the maximum currents. The cerebral voxels show limited sensitivity of the induced electric field to changes in conductivity and permittivity, whereas the field varies approximately linearly with frequency. These findings illustrate the importance of including each of the above parameters in the model and confirm the need for accuracy in the applied patient-specific method, which can be used in computer-assisted TMS.

Bounds on quantum confinement effects in metal nanoparticles

NASA Astrophysics Data System (ADS)

Blackman, G. Neal; Genov, Dentcho A.

2018-03-01

Quantum size effects on the permittivity of metal nanoparticles are investigated using the quantum box model. Explicit upper and lower bounds are derived for the permittivity and relaxation rates due to quantum confinement effects. These bounds are verified numerically, and the size dependence and frequency dependence of the empirical Drude size parameter is extracted from the model. Results suggest that the common practice of empirically modifying the dielectric function can lead to inaccurate predictions for highly uniform distributions of finite-sized particles.

Measurement and modeling of dielectric properties of Pb(Zr,Ti)O3 ferroelectric thin films.

PubMed

Renoud, Raphaël; Borderon, Caroline; Gundel, Hartmut W

2011-09-01

In this study, the real and imaginary parts of the complex permittivity of lead zirconate titanate ferroelectric thin films are studied in the frequency range of 100 Hz to 100 MHz. The permittivity is well fitted by the Cole-Cole model. The variation of the relaxation time with the temperature is described by the Arrhenius law and an activation energy of 0.38 eV is found. Because of its nonlinear character, the dielectric response of the ferroelectric sample depends on the amplitude of the applied ac electric field. The permittivity is composed of three different contributions: the first is due to intrinsic lattice, the second is due to domain wall vibrations, and the third is due to domain wall jumps between pinning centers. This last contribution depends on the electric field, so it is important to control the field amplitude to obtain the desired values of permittivity and tunability.

Dielectric relaxation in AgI doped silver selenomolybdate glasses

NASA Astrophysics Data System (ADS)

Palui, A.; Shaw, A.; Ghosh, A.

2016-05-01

We report the study of dielectric properties of some silver ion conducting silver selenomolybdate mixed network former glasses in a wide frequency and temperature range. The experimental data have been analyzed in the framework of complex dielectric permittivity. The dielectric permittivity data have been well interpreted using the Cole-Cole function. The temperature dependence of relaxation time obtained from real part of dielectric permittivity data shows an Arrhenius behavior. The activation energy shows a decreasing trend with the increase of doping content. Values of stretched exponential parameter are observed to be independent of temperature and composition.

Electrode effects in dielectric spectroscopy measurements on (Nb+In) co-doped TiO2

NASA Astrophysics Data System (ADS)

Crandles, D. A.; Yee, S. M. M.; Savinov, M.; Nuzhnyy, D.; Petzelt, J.; Kamba, S.; Prokeš, J.

2016-04-01

Recently, several papers reported the discovery of giant permittivity and low dielectric loss in (Nb+In) co-doped TiO2. A series of tests was performed which included the measurement of the frequency dependence of the dielectric permittivity and alternating current (ac) conductivity of co-doped (Nb+In)TiO2 as a function of electrode type, sample thickness, and temperature. The data suggest that the measurements are strongly affected by the electrodes. The consistency between four-contact van der Pauw direct current conductivity measurements and bulk conductivity values extracted from two-contact ac conductivity measurements suggest that the values of colossal permittivity are, at least in part, a result of Schottky barrier depletion widths that depend on electrode type and temperature.

Electrode effects in dielectric spectroscopy measurements on (Nb +In) co-doped TiO2

NASA Astrophysics Data System (ADS)

Crandles, David; Yee, Susan; Savinov, Maxim; Nuzhnyy, Dimitri; Petzelt, Jan; Kamba, Stanislav; Prokes, Jan

Recently, several papers reported the discovery of giant permittivity and low dielectric loss in (Nb+In) co-doped TiO2. A series of tests was performed which included the measurement of the frequency dependence of the dielectric permittivity and ac conductivity of co-doped (Nb+In)TiO2 as a function of electrode type, sample thickness and temperature. The data suggest that the measurements are strongly affected by the electrodes. The consistency between four contact van der Pauw dc conductivity measurements and bulk conductivity values extracted from two contact ac conductivity measurements suggest that the values of colossal permittivity are, at least in part, a result of Schottky barrier depletion widths that depend on electrode type and temperature. Nserc, Czech Science Foundation (Project 15-08389S).

Radio frequency and capacitive sensors for dielectric characterization of low-conductivity media

NASA Astrophysics Data System (ADS)

Sheldon, Robert T.

Low-conductivity media are found in a vast number of applications, for example as electrical insulation or as the matrix polymer in high strength-to-weight ratio structural composites. In some applications, these materials are subjected to extreme environmental, thermal, and mechanical conditions that can affect the material's desired performance. In a more general sense, a medium may be comprised of one or more layers with unknown material properties that may affect the desired performance of the entire structure. It is often, therefore, of great import to be able to characterize the material properties of these media for the purpose of estimating their future performance in a certain application. Low-conductivity media, or dielectrics, are poor electrical conductors and permit electromagnetic waves and static electric fields to pass through with minimal attenuation. The amount of electrical energy that may be stored (and lost) in these fields depends directly upon the material property, permittivity, which is generally complex, frequency-dependent and has a measurable effect on sensors designed to characterize dielectric media. In this work, two different types of dielectric sensors: radio frequency resonant antennas and lower-frequency (<1 MHz) capacitive sensors, are designed for permittivity characterization in their respective frequency regimes. In the first part of this work, the capability of characterizing multilayer dielectric structures is studied using a patch antenna, a type of antenna that is primarily designed for data communications in the microwave bands but has application in the field of nondestructive evaluation as well. Each configuration of a patch antenna has a single lowest resonant (dominant mode) frequency that is dependent upon the antenna's substrate material and geometry as well as the permittivity and geometry of exterior materials. Here, an extant forward model is validated using well-characterized microwave samples and a new method of resonant frequency and quality factor determination from measured data is presented. Excellent agreement between calculated and measured values of sensor resonant frequency was obtained for the samples studied. Agreement between calculated and measured quality factor was good in some cases but incurred the particular challenge of accurately quantifying multiple contributions to loss from the sensor structure itself, which at times dominates the contribution due to the sample material. Two later chapters describe the development of capacitive sensors to quantify the low-frequency changes in material permittivity due to environmental aging mechanisms. One embodiment involves the application of coplanar concentric interdigital electrode sensors for the purpose of investigating polymer-matrix degradation in glass-fiber composites due to isothermal aging. Samples of bismaleimide-matrix glass-fiber composites were aged at several high temperatures to induce thermal degradation and capacitive sensors were used to measure the sensor capacitance and dissipation factor, parameters that are directly proportional to the real and imaginary components of complex permittivity, respectively. It was shown that real permittivity and dissipation factor decreased with increasing aging temperature, a trend that was common to both interdigital sensor measurements and standard parallel plate electrode measurements. The second piece of work involves the development of cylindrical interdigital electrode sensors to characterize complex permittivity changes in wire insulation due to aging-related degradation. The sensor was proven effective in detecting changes in irradiated nuclear power plant wiring insulation and in aircraft wiring insulation due to liquid chemical immersion. In all three cases, the results indicate a clear correlation of measured capacitance and dissipation factor with increased degradation.

Dynamical properties of epitaxial ferroelectric superlattices

NASA Astrophysics Data System (ADS)

Kim, Y.; Gerhardt, R. A.; Erbil, A.

1997-04-01

The dynamical properties of epitaxial ferroelectric heterostructures have been investigated by studying the dielectric behavior under external electric field. A phenomenon with a giant permittivity was observed. At low frequencies, real permittivities as high as 420 000 have been measured. Real and imaginary parts of the dielectric constant show large dispersion at high frequencies. In dc measurements, a nonlinear resistance is observed with a well-defined threshold field, correlating with the dc bias-field dependence of ac permittivities. We model these observations as a result of the motion of pinned domain-wall lattices, having sliding-mode motion at high electric fields. The good agreement between the experimental and theoretical results suggests that the deposited interdigitated electrode pattern plays a crucial role in controlling domain-wall dynamics. The pinning of the domain wall comes from a nucleation barrier to the creation of new domain walls.

[Experimental research and analysis on dielectric properties of blood in anemia mice].

PubMed

Shen, Ben; Liang, Quiyan; Gao, Weiqi; You, Chu; Hong, Mengqi; Ma, Qing

2013-12-01

The conductivity and permittivity of blood in mice were measured by the AC electrical impedance method at frequency range of 0.1-100MHz, and then the changes of the Cole-Cole parameters of dielectric spectra of blood from phenylhydrazine-induced anemia mice were observed by numerical calculation and curve fitting residual analysis of the Cole-Cole equation. The results showed that hematocrit (Hct) of the mice with phenylhydrazine injection was significantly reduced; the permittivity(epsilon) spectroscopy of blood moved to the low insulating region and its permittivity decreased; conductivity (kappa) spectrum curve of blood moved to the high conductivity zone and conductivity increased; the 2nd characteristic frequency was lower than that in the normal group. There was phenylhydrazine dose dependent in the changes of the Cole-Cole parameters of dielectric spectra of blood.

Monomer Derived Poly(Furfuryl)/BaTiO3 0-3 Nanocomposite Capacitors: Maximization of the Effective Permittivity Through Control at the Interface.

PubMed

Pearsall, Frederick A; Lombardi, Julien; O'Brien, Stephen

2017-11-22

Frequency stable, high permittivity nanocomposite capacitors produced under mild processing conditions offer an attractive replacement to MLCCs derived from conventional ceramic firing. Here, 0-3 nanocomposites were prepared using gel-collection derived barium titanate nanocrystals, suspended in a poly(furfuryl alcohol) matrix, resulting in a stable, high effective permittivity, low loss dielectric. The nanocrystals are produced at 60 °C, emerging as fully crystallized cubic BTO, 8 nm, paraelectric with a highly functional surface that enables both suspension and chemical reaction in organic solvents. The nanocrystals were suspended in furfuryl alcohol inside a uniquely prepared mold, in which volume fraction of nanocrystal filler (ν f ) could be varied. Polymerization of the matrix in situ at 70-90 °C resulted in a nanocomposite with a higher than anticipated effective permittivity (up to 50, with ν f only 0.41, 0.5-2000 kHz), exceptional stability as a function of frequency, and very favorable dissipation factors (tan δ < 0.01, ν f < 0.41; tan δ < 0.05, ν f < 0.5). The increased permittivity is attributed to the covalent attachment of the poly(furfuryl alcohol) matrix to the surface of the nanocrystals, homogenizing the particle-matrix interface, limiting undercoordinated surface sites and reducing void space. XPS and FTIR confirmed strong interfacial interaction between matrix and nanocrystal surface. Effective medium approximations were used to compare this with similar nanocomposite systems. It was found that the high effective permittivity could not be attributed to the combination of two components alone, rather the creation of a hybrid nanocomposite possessing its own dielectric behavior. A nondispersive medium was selected to focus on the frequency dependent permittivity of the 8 nm barium titanate nanocrystals. Experimental corroboration with known theory is evident until a specific volume fraction (ν f ≈ 0.3) where, due to a sharp increase in the effective permittivity, approximations fail to adequately describe the nanocomposite medium.

Wireless network of stand-alone end effect probes for soil in situ permittivity measurements over the 100MHZ-6GHz frequency range

NASA Astrophysics Data System (ADS)

Demontoux, François; Bircher, Simone; Ruffié, Gilles; Bonnaudiin, Fabrice; Wigneron, Jean-Pierre; Kerr, Yann

2017-04-01

Microwave remote sensing and non-destructive analysis are a powerful way to provide properties estimation of materials. Numerous applications using microwave frequency behavior of materials (remote sensing above land surfaces, non-destructive analysis…) are strongly dependent on the material's permittivity (i.e. dielectric properties). This permittivity depends on numerous parameters such as moisture, texture, temperature, frequency or bulk density. Permittivity measurements are generally carried out in the laboratory. Additionally, dielectric mixing models allow, over a restricted range of conditions, the assessment of a material's permittivity. in-situ measurements are more difficult to obtain. Some in situ measurement probes based on permittivity properties of soil exist (e.g. Time Domain Reflectometers and Transmissometers, capacitance and impedance sensors). They are dedicated to the acquisition of soil moisture data based on permittivity (mainly the real part) estimations over a range of frequencies from around 50 MHz to 1 or 2 GHz. Other Dielectric Assessment Kits exist but they are expensive and they are rather dedicated to laboratory measurements. Furthermore, the user can't address specific issues related to particular materials (e.g. organic soils) or specific measurement conditions (in situ long time records). At the IMS Laboratory we develop probes for in situ soil permittivity measurements (real and imaginary parts) in the 0.5 - 6 GHz frequency range. They are based on the end effect phenomenon of a coaxial waveguide and so are called end effect probes in this paper. The probes can be connected to a portable Vector Network Analyzer (VNA, ANRITSU MS2026A) for the S11 coefficient measurements needed to compute permittivity. It is connected to a PC to record data using an USB connection. This measurement set-up is already used for in situ measurement of soil properties in the framework of the European Space Agency's (ESA) SMOS space mission. However, it should be useful to install many probes on the same site to obtain permittivity measurements over a large area. To reach this goal, the probes should communicate with each other to send data to a record device. Furthermore, it is needed to record measurements over a long time period (many months) to study the in-situ dielectric soil property variations according to changing weather conditions and seasonal trends. The goal of the research work presented is to develop a dielectric sensor system based on end effect probes able to communicate the data using wireless technology. It must be stand-alone from an electric and data recording point of view so it must integrate a VNA circuit instead of the ANRITSU VNA used for the moment. The LoRa wireless technology has been selected because of its low electric consumption and the large distance between equipment available. LoRaWAN™ is a Low Power Wide Area Network specification intended for wireless battery operated devices. The LoRaWAN data rates range from 0.3 kbps to 50 kbps which is sufficient for our probes' data exchanges. We will present the work done to perform the VNA and the LoRa communication board as well as the work done to improve the probes and the permittivity computation algorithm.

Electrical properties of dispersions of graphene in mineral oil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monteiro, O. R., E-mail: othon.monteiro@bakerhughes.com

2014-02-03

Dispersions of graphene in mineral oil have been prepared and electrical conductivity and permittivity have been measured. The direct current (DC) conductivity of the dispersions depends on the surface characteristics of the graphene platelets and followed a percolation model with a percolation threshold ranging from 0.05 to 0.1 wt. %. The difference in DC conductivities can be attributed to different states of aggregation of the graphene platelets and to the inter-particle electron transfer, which is affected by the surface radicals. The frequency-dependent conductivity (σ(ω)) and permittivity (ε(ω)) were also measured. The conductivity of dispersions with particle contents much greater than themore » percolation threshold remains constant and equal to the DC conductivity at low frequencies ω with and followed a power-law σ(ω)∝ ω{sup s} dependence at very high frequencies with s≈0.9. For dispersions with graphene concentration near the percolation threshold, a third regime was displayed at intermediate frequencies indicative of interfacial polarization consistent with Maxwell-Wagner effect typically observed in mixtures of two (or more) phases with very distinct electrical and dielectric properties.« less

Grain size effect on the permittivity of La1.5Sr0.5NiO4 nanoparticles

NASA Astrophysics Data System (ADS)

Dang Thanh, Tran; Van Hong, Le

2009-09-01

Using the annealing at different temperatures the La1.5Sr0.5NiO4 ceramic samples with different mean grain size were manufactured. Mean grain size () of the samples was evaluated by Warren-Averbach method and their SEM images. The obtained results of both methods are almost the same, changing from 16.2 to 95 nm in dependence on the annealing temperature. The frequency dependence of dielectric constant in the frequency range of (1-13 MHz) was recorded for all samples. The real (ɛ') and the imaginary parts (ɛ") of the permittivity of La1.5Sr0.5NiO4 samples abnormally depend on the frequency, exhibiting a dielectric resonance around 500 kHz. R-L-C in series equivalent-circuit fitted well for the obtained result. It was supposed that there exists magnetic contribution in material that suggests the material is a multiferroic one. Dependence of the (ɛ') on the mean grain size supposed that the colossal dielectric property is an intrinsic behaviour of La1.5Sr0.5NiO4 material.

Measurements in Vacuum of the Effect of Ilmenite on the Complex Dielectric Permittivity of Planetary Regolith Analog Materials

NASA Astrophysics Data System (ADS)

Boivin, A.; Hickson, D.; Cunje, A.; Tsai, C. A.; Ghent, R. R.; Daly, M. G.

2016-12-01

When considering radar observations of airless bodies containing regolith, the radar backscattering coefficient is dependent on both the complex permittivity and the thickness of the regolith. The complex permittivity is typically normalized by the permittivity of free space (ɛ0) and reported as the relative permittivity (ɛr = ɛr' + iɛr'', where ɛr' is the dielectric constant and ɛr'' is the loss factor). Given the backscattering coefficient and the dielectric properties of the regolith, it should be possible to determine regolith thickness. This problem has long been considered for the Moon and many measurements of either real or complex permittivity have been made on both Apollo samples and regolith analogues. Measurements thus far have either only been done at a lower frequency range (< 1GHz) than both S Band and X Band radar or did not systematically explore the relationship between complex permittivity and the mineral content. Measurements of geological materials at higher frequencies are, for example, useful for Arecibo S Band (2.38 GHz) as well as Mini-RF X Band (7.14 GHz) Lunar observations, future RIMFAX GPR data from Mars 2020 (150 MHz - 1.2 GHz), and other future radar data at higher frequencies. Systematically exploring the relationship between complex permittivity of regolith and its mineralogical content is particularly relevant for missions to asteroids, such as the OSIRIS-REx mission to (101955) Bennu, where the composition of soil is as of yet unknown. For Lunar materials the presence of the mineral ilmenite (FeTiO3), which contains equal portions FeO and TiO2, is thought to be the dominant factor to control the loss tangent (tanδ, the ratio of ɛr'' to ɛr'). As a starting point into our investigation of the effects of mineralogy on these properties, we present results of dielectric permittivity measurements using a coaxial transmission line in vacuum, which aim to determine the effects of various amounts of ilmenite on the loss tangent of powdered materials. In order to remove moisture from our samples, powders are baked at 250°C for 48hrs and are then placed in a vacuum chamber. Measurements are then made using a sweep of frequencies from 300 kHz to 8.5 GHz. Preliminary results show that ilmenite significantly influences signal attenuation, especially at high concentrations.

Size-dependent Hamaker constants for silver and gold nanoparticles

NASA Astrophysics Data System (ADS)

Pinchuk, Pavlo; Jiang, Ke

2015-08-01

Hamaker-Lifshitz constants are material specific constants that are used to calculate van der Waals interaction forces between small particles in solution. Typically, these constants are size-independent and material specific. According to the Lifshitz theory, the Hamaker-Lifshitz constants can be calculated by taking integrals that include the dielectric permittivity, as a function of frequency, of the interacting particles and the medium around particles. The dielectric permittivity of interacting metal nanoparticles can be calculated using the Drude model, which is based on the assumption of motion of free conducting electrons. For bulk metals, the Drude model does not predict any sizedependence of the dielectric permittivity. However, the conducting electrons in small noble metal nanoparticles (R ~ 10nm) exhibit surface scattering, which changes the complex permittivity function. In this work, we show theoretically that scattering of the free conducting electrons inside silver and gold nanoparticles with the size of 1 - 50 nm leads to size-dependent dielectric permittivity and Hamaker-Lifshitz constants. We calculate numerically the Hamaker-Lifshitz constants for silver and gold nanoparticles with different diameters. The results of the study might be of interests for understanding colloidal stability of metal nanoparticles.

Microwave dielectric measurements of lunar soil with a coaxial line resonator method

NASA Technical Reports Server (NTRS)

Bussey, H. E.

1979-01-01

A method is given for sensitive dielectric measurements at a series of microwave frequencies using a section of coaxial line. The line is used as a 1-port cavity resonator; it resonates when the electrical length of the center conductor equals 1, 2 . . . , N half-wave lengths. The dielectric properties of an Apollo 17 dried soil sample were measured in vacuum over a temperature range of 173 to 373 K. The relative permittivity and the loss tangent were determined and the frequency dependence was very small. The derivative with respect to temperature, per degree, was 0.00045 for the permittivity and 0.00002 for the loss tangent.

Analytical and experimental procedures for determining propagation characteristics of millimeter-wave gallium arsenide microstrip lines

NASA Technical Reports Server (NTRS)

Romanofsky, Robert R.

1989-01-01

In this report, a thorough analytical procedure is developed for evaluating the frequency-dependent loss characteristics and effective permittivity of microstrip lines. The technique is based on the measured reflection coefficient of microstrip resonator pairs. Experimental data, including quality factor Q, effective relative permittivity, and fringing for 50-omega lines on gallium arsenide (GaAs) from 26.5 to 40.0 GHz are presented. The effects of an imperfect open circuit, coupling losses, and loading of the resonant frequency are considered. A cosine-tapered ridge-guide text fixture is described. It was found to be well suited to the device characterization.

Dielectric and microstructure properties of polymer carbon black composites

NASA Astrophysics Data System (ADS)

Brosseau, C.; Boulic, F.; Queffelec, P.; Bourbigot, C.; Le Mest, Y.; Loaec, J.; Beroual, A.

1997-01-01

Dielectric and physicochemical properties of a composite material prepared by incorporating carbon black particles into a polymer matrix were investigated. Two types of carbon blacks, having very different structures of aggregates, were used. The volume fraction of the carbon blacks ranged from 0.2% to 7%, i.e. below and above the percolation threshold concentration observed from the measurements of dc conductivity. The composite samples were characterized in terms of: swelling by a compatible solvent, electron paramagnetic resonance (EPR) response, and frequency variation of permittivity. First, the article attempts to evaluate the diffusion coefficient of an appropriate solvent in these materials. Sorption kinetics experiments with toluene indicate that the initial uptake of solvent exhibits a square root dependence in time as a consequence of Fick's law and permit to evaluate the effective diffusion coefficient in the range 10-11-10-12 m2 s-1 depending on the volume fraction of the carbon black in the sample. Second, the analysis of the carbon black concentration dependence of the intensity and linewidth of the EPR signals indicates that EPR is an important experimental probe of the structure of the elasticity network. The most notable feature of the present work is that we find a correlation of the percolation threshold concentration which is detected from the dc electrical conductivity with moments of the EPR lines. The conclusions on the elasticity networks deduced from swelling measurements are confirmed by EPR data carried out on swollen samples. On qualitative grounds the role of the specific surface of carbon black is further analyzed. It is suggested that the elasticity network is mainly controlled by secondary (respectively primary) aggregates for samples containing low (respectively high) specific surface carbon blacks. Last, the article reports precise experimental data on the permittivity of these composite materials as a function of frequency. Thanks to a sensitive measurement technique using an impedance analyzer, we are able to measure the complex permittivity and permeability values of the samples in the frequency range from 108 to 1010 Hz. It is found that the real part of the permittivity is a function of frequency f, via a power law expression ɛ'=af-b, where a and b are two parameters depending upon carbon black concentration, in the range of frequency investigated. The data analysis reaffirms the result that percolation threshold is a key parameter for characterizing the topological arrangement in these structures.

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

Monitoring of cell and tissue responses to photodynamic therapy by electrical impedance spectroscopy

NASA Astrophysics Data System (ADS)

Molckovsky, A.; Wilson, B. C.

2001-04-01

Electrical impedance spectroscopic (EIS) monitoring of photodynamic therapy (PDT) was investigated in vivo in rat liver and in vitro in multicellular spheroids. Liver impedance was continuously measured with two needle electrodes before, during and up to 3 hours following Photofrin-PDT. EIS spectra were altered immediately after PDT, with significant changes in conductivity at ~10 kHz, and in permittivity at ~30 kHz and 1 MHz. The change in permittivity at high frequencies was related to oedema, while low-frequency effects were attributed to cell necrosis and vascular changes. Photofrin-PDT-treated spheroids showed dose-dependent decreases in permittivity and conductivity at frequencies above 10 and 100 kHz, respectively. Histology showed concomitant development of a damaged rim containing sparsely distributed cells with compromised membranes and lightly staining cytoplasm. Different EIS responses to apoptotic versus necrotic modes of cell death further verified the sensitivity of impedance to purely cellular changes in the spheroid model. In conclusion, EIS sensitivity to PDT-induced damage, at both the cell and tissue level, varies with dose and time, and can be correlated qualitatively to biological changes.

Dielectric spectroscopy of solutions of amino silicone emulsion in distilled water

NASA Astrophysics Data System (ADS)

Shah, K. N.; Rana, V. A.; Trivedi, C. M.; Vankar, H. P.

2016-05-01

Complex permittivity spectra ɛ*(ω) = ɛ' - jɛ″ of solutions of amino silicone emulsion in distilled water in the frequency range 100 Hz to 2 MHz were obtained using precision LCR meter. Complex permittivity data is used to find out complex impedance z*(ω) and complex electric conductivity σ*(ω). All these spectra are used to gain information about various polarization processes taking place in the solutions of amino silicone emulsion in distilled water under the effect of ac electric field. The frequency and concentration dependent behavior of the solutions of amino silicone emulsion in distilled waterhave beenalso investigated. Density and refractive index of the samples are also measured and are reported.

Dielectric studies of the paracetamol-lenticular tissue interactions.

PubMed

Marzec, E; Olszewski, J; Grześkowiak, E; Kamińska, A; Bienert, A; Iwanik, K

2011-05-01

This paper reports on the effect of paracetamol on the dielectric behavior of the rabbit lens. Measurements were performed over the frequency range of 100 Hz-100 kHz in air and at the temperature of 35°C. The frequency dependencies of the relative permittivity and dielectric loss for the control and paracetamol-control lenses are described in terms of a power-low, Debye and Cole-Cole relations. The effect of paracetamol on the dielectric properties of the lens is visible in the lower values of the relative permittivity than those for the control sample at the same frequency. In addition, the relaxations around 18 and 46 kHz for the paracetamol-control lens are shifted to lower frequencies compared with the control lens. The results of this work indicate that the present method is useful in detection of the lens toxicity elicited by overdoses of paracetamol in animal. Copyright © 2010 Elsevier B.V. All rights reserved.

Development of numerical phantoms by MRI for RF electromagnetic dosimetry: a female model.

PubMed

Mazzurana, M; Sandrini, L; Vaccari, A; Malacarne, C; Cristoforetti, L; Pontalti, R

2004-01-01

Numerical human models for electromagnetic dosimetry are commonly obtained by segmentation of CT or MRI images and complex permittivity values are ascribed to each issue according to literature values. The aim of this study is to provide an alternative semi-automatic method by which non-segmented images, obtained by a MRI tomographer, can be automatically related to the complex permittivity values through two frequency dependent transfer functions. In this way permittivity and conductivity vary with continuity--even in the same tissue--reflecting the intrinsic realistic spatial dispersion of such parameters. A female human model impinged by a plane wave is tested using finite-difference time-domain algorithm and the results of the total body and layer-averaged specific absorption rate are reported.

Broadband permittivity measurements on porous planetary regoliths simulants, in relation with the Rosetta mission to 67P/C-G

NASA Astrophysics Data System (ADS)

Brouet, Yann; Levasseur-Regourd, Anny-Chantal; Encrenaz, Pierre; Sabouroux, Pierre; Heggy, Essam; Kofman, Wlodek; Thomas, Nick

2015-04-01

The Rosetta mission has successfully rendezvous comet 67P/Churyumov-Gerasimenko (hereafter 67P) last year and landed Philae module on its nucleus on 12 November it 2014. Among instruments onboard Rosetta, MIRO [1], composed of two radiometers, with receivers at 190 GHz and 563 GHz (center-band), is dedicated to the measurements of the subsurface and surface brightness temperatures. These values depend on the complex relative permittivity (hereafter permittivity) with ɛ' and ɛ'' the real and imaginary parts. The permittivity of the material depends on frequency, bulk density/porosity, composition and temperature [2]. Considering the very low bulk density of 67P nucleus (about 450 kg.m-3 [3]) and the suspected presence of a dust mantle in many areas of the nucleus [4], investigations on the permittivity of porous granular samples are needed to support the interpretation of MIRO data, as well as of other microwave experiments onboard Rosetta, e.g. CONSERT [5], a bistatic penetrating radar working at 90 MHz. We have developed a programme of permittivity measurements on porous granular samples over a frequency range from 50 MHz to 190 GHz under laboratory conditions (e.g. [6] and [7]). We present new results obtained on JSC-1A lunar soil simulant and ashes from Etna. The samples were split into several sub-samples with different size ranges covering a few to 500 μm. Bulk densities of the sub-samples were carefully measured and found to be in the 800-1400 kg.m-3 range. Sub-samples were also dried and volumetric moisture content was found to be below 0.6%. From 50 MHz to 6 GHz and at 190 GHz, the permittivity has been determined, respectively with a coaxial cell and with a quasi-optical bench mounted in transmission, both connected to a vector network analyzer. The results demonstrate the dispersive behaviours of ɛ' between 50 MHz and 190 GHz. Values of ɛ' remain within the 3.9-2.6 range for all sub-samples. At CONSERT frequency, ɛ'' is within the 0.01-0.09 range for all sub-samples. The single-relaxation Debye model fits relatively well the global behaviour of ɛ' over the frequency range, thus validating the experimental setups and measurements obtained. Furthermore, results confirm that ɛ' decreases quasi-linearly with the decreasing bulk density at any frequency, as expected by the mixing formulae. Taking into account possible temperature variations within 67P nucleus [8] and the linear decrease of the permittivity with the temperature, as measured by [9] on JSC-1A sample, these results indicate that, on the near-surface of 67P covered by a free-ice dust mantle at the frequencies of MIRO and CONSERT, ɛ' is likely to be in the 1.1-1.8 range and ɛ'' is likely to be below 0.05. [1]Gulkis et al. (2007) SSR, 128, 561. [2]Ulaby. and Long D. (2014) Univ. Michigan Press. [3]Sierks et al. (2015), in prep. [4]Thomas et al. (2015), in prep. [5]Kofman et al. (2007) SSR, 128, 413. [6]Brouet (2013), PhD Thesis, Univ. P. & M. Curie. [7]Brouet et al. (2014) PSS, 103, 143. [8]De Sanctis et al. (2005), A&A, 444, 605. [9]Calla & Rathore (2012), ASR, 50, 1607

Standardized UXO Technology Demonstration Site, Scoring Record No. 928

DTIC Science & Technology

2011-03-01

magnetic permittivity (possibly complex and frequency dependent), ω is radian frequency, Vrx is the voltage at the receiver coil, txn̂ and rxn̂ are the...voltage induced in the receiver coil Vrx due to the induced target dipole moment m  is related to magnetic field uxoH  at the target due to a

Invariants of electromechanical coupling coefficients in piezoceramics.

PubMed

Mezheritsky, Alex V

2003-12-01

The relationships between coefficients of electromechanical coupling (CEMC) of various types of piezoceramic resonator (PR) vibrations are considered. Being constant for a given piezoceramic state, the range of variation of piezoceramics dielectric permittivity from a mechanically "free" condition at relatively low frequencies up to an "overall clamped" condition at high frequencies is determined by a consecutive "clamping", caused by a complex of CEMCs of various particular vibrational modes peculiar to the resonator. As the difference between "free" and "overall clamped" permittivities is always determined by the maximal piezomaterial ki3 coupling coefficient, the difference does not depend on the path that was gone through the low-high frequency range, which includes all the vibrational modes possible for a particular PR. The influence of the piezoelectric and elastic anisotropy of lead-zirconate-titanate (PZT) piezoceramic materials on relative CEMC variations was experimentally investigated.

Monitoring processing properties of high performance thermoplastics using frequency dependent electromagnetic sensing

NASA Technical Reports Server (NTRS)

Kranbuehl, D. E.; Delos, S. E.; Hoff, M. S.; Weller, L. W.; Haverty, P. D.

1987-01-01

An in situ NDE dielectric impedance measurement method has been developed for ascertaining the cure processing properties of high temperature advanced thermoplastic and thermosetting resins, using continuous frequency-dependent measurements and analyses of complex permittivity over 9 orders of magnitude and 6 decades of frequency at temperatures up to 400 C. Both ionic and Debye-like dipolar relaxation processes are monitored. Attention is given to LARC-TPI, PEEK, and poly(arylene ether) resins' viscosity, glass transition temperature, recrystallization, and residual solvent content and evolution properties.

A large coaxial reflection cell for broadband dielectric characterization of coarse-grained materials

NASA Astrophysics Data System (ADS)

Bore, Thierry; Bhuyan, Habibullah; Bittner, Tilman; Murgan, Vignesh; Wagner, Norman; Scheuermann, Alexander

2018-01-01

Knowledge of the frequency-dependent electromagnetic properties of coarse-grained materials is imperative for the successful application of high frequency electromagnetic measurement techniques for near and subsurface monitoring. This paper reports the design, calibration and application of a novel one-port large coaxial cell for broadband complex permittivity measurements of civil engineering materials. It was designed to allow the characterization of heterogeneous material with large aggregate dimensions (up to 28 mm) over a frequency range from 1 MHz-860 MHz. In the first step, the system parameters were calibrated using the measured scattering function in a perfectly known dielectric material in an optimization scheme. In the second step, the method was validated with measurements made on standard liquids. Then the performance of the cell was evaluated on a compacted coarse-grained soil. The dielectric spectra were obtained by means of fitting the measured scattering function using a transverse electromagnetic mode propagation model considering the frequency-dependent complex permittivity. Two scenarios were systematically analyzed and compared. The first scenario consisted of a broadband generalized dielectric relaxation model with two Cole-Cole type relaxation processes related to the interaction of the aqueous phase and the solid phase, a constant high frequency contribution as well as an apparent direct current conductivity term. The second scenario relied on a three-phase theoretical mixture equation which was used in a forward approach in order to calibrate the model. Both scenarios provide almost identical results for the broadband effective complex relative permittivity. The combination of both scenarios suggests the simultaneous estimation of water content, density, bulk and pore water conductivity for road base materials for in situ applications.

The importance of the solids loading on confirming the dielectric nanosize dependence of BaTiO₃ powders by slurry method.

PubMed

Zhou, Wei; Nie, Yi Mei; Li, Shu Jing; Liang, Hai Yan

2013-01-01

The dielectric nanosize dependence of BaTiO₃ powders was investigated by the slurry method, where two series of BaTiO₃ slurries with 10 vol% and 30 vol% solids loadings were prepared as model samples. Applying the Bruggeman-Hanai equation, the high-frequency limiting permittivity (ε(h)) of the slurries was extracted from the dielectric spectra. The ε(h) of the 10 vol% slurry showed abnormal size independence in the range from 100 nm to 700 nm, and the ε(h) of the 30 vol% slurry exhibited good agreement with the previous prediction. Through analysing quantitatively the response of ε(h) to the changing permittivity of the powders under different solids loading, it was found that the ε h of the slurry with lower solids loading is more inclined to be interfered by the systematic and random errors. Furthermore, a high permittivity value was found in the BaTiO₃ powders with 50 nm particle size.

Dielectric properties of binary mixtures of ethylene glycol monophenyl ether and methanol

NASA Astrophysics Data System (ADS)

Vaghela, K. C.; Vankar, H. P.; Trivedi, C. M.; Rana, V. A.

2017-05-01

Static permittivity (ɛ0) and permittivity at optical frequency (ɛ∞) of ethylene glycol monophenyl ether (EGMPE), methanol (MeOH) and their binary mixtures of varying concentrations have been measured at room temperature (T=299.15 K). The investigation showed a systematic change in permittivity with change in concentration of MeOH in binary mixture system. Measured data have been used to calculate the various dielectric parameters such as E E excess static permittivity (ɛ0E), excess permittivity at optical frequency (ɛ∞E) and Bruggeman factor (fB). Determined parameters provided some information about the molecular interaction among the molecular species of the binary mixtures.

Dielectric relaxation of selenium-tellurium mixed former glasses

NASA Astrophysics Data System (ADS)

Palui, A.; Ghosh, A.

2017-05-01

We report the study of dielectric properties of mixed network former glasses of composition 0.3Ag2O-0.7(xSeO2-(1-x)TeO2); x=0, 0.1, 0.3, 0.4, 0.5 and 0.6 in a wide frequency 10 Hz - 2 MHz and temperature range 223 K - 403 K. The experimental data have been analyzed in the framework of complex dielectric permittivity. The dielectric permittivity data have been analyzed using the Cole-Cole function. The inverse temperature dependence of relaxation time obtained from real part of dielectric permittivity data follows the Arrhenius relation. The activation energy shows mixed glass former effect with variation of mixed former ratio. A non-zero value of shape parameters is observed and it is almost independent of temperature and composition.

Dielectric coagulometry: a new approach to estimate venous thrombosis risk.

PubMed

Hayashi, Yoshihito; Katsumoto, Yoichi; Omori, Shinji; Yasuda, Akio; Asami, Koji; Kaibara, Makoto; Uchimura, Isao

2010-12-01

We present dielectric coagulometry as a new technique to estimate the risk of venous thrombosis by measuring the permittivity change associated with the blood coagulation process. The method was first tested for a simple system of animal erythrocytes suspended in fibrinogen solution, where the coagulation rate was controlled by changing the amount of thrombin added to the suspension. Second, the method was applied to a more realistic system of human whole blood, and the inherent coagulation process was monitored without artificial acceleration by a coagulation initiator. The time dependence of the permittivity at a frequency around 1 MHz showed a distinct peak at a time that corresponds to the clotting time. Our theoretical modeling revealed that the evolution of heterogeneity and the sedimentation in the system cause the peak of the permittivity.

Study of excess dielectric properties and Kirkwood correlation parameter of binary mixtures of benzaldehyde and methanol at different temperatures

NASA Astrophysics Data System (ADS)

Shah, N. S.; Vankar, H. P.; Rana, V. A.

2018-05-01

Static permittivity (ɛ0) and permittivity at optical frequency (ɛ∞) of the Benzaldehyde (BZ), Methanol (MeOH) and their binary mixtures were measured in the temperature range from 293.15 K to 323.15 K (in the interval of 10 K). From the ɛ0 and ɛ∞ other parameters such as effective Kirkwood correlation factor (geff), corrective Kirkwood correction factor (gf), Bruggman factor (fB), excess permittivity (ɛ0E ) and permittivity at optical frequency (ɛ∞E ) were evaluated.

Giant dielectric permittivity and weak ferromagnetic behavior in Bi{sub 0.5}La{sub 0.5}Fe{sub 0.5}Cr{sub 0.5}O{sub 3} ceramic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tirupathi, Patri; Raju, K.; Peetla, Naresh

A pervoskite (Bi{sub 0.5}La{sub 0.5})(Fe{sub 0.5}Cr{sub 0.5})O{sub 3} (BLFC) nanoparticles were synthesized by high energy ball milling. Rietveld refined X-ray diffraction studies revealed that this compound shows orthorhombic structure with Pbnm space group. The dielectric studies were investigated in wide frequency (10{sup 2}-10{sup 6}) range indicating giant dielectric permittivity behavior similar to LaFeO{sub 3} ceramic. The noted dielectric loss relaxation frequency dependent is as following the Arrhenius law can be ascribed as polaronic conduction. Further, magnetic transition at around 337 K and coexistence of weak ferromagnetic and antiferromagnetic behavior is observed below magnetic transition.

Study of variability of permittivity and its mapping over lunar surface and subsurface using multisensors datasets

NASA Astrophysics Data System (ADS)

Calla, O. P. N.; Mathur, Shubhra; Gadri, Kishan Lal; Jangid, Monika

2016-12-01

In the present paper, permittivity maps of equatorial lunar surface are generated using brightness temperature (TB) data obtained from Microwave Radiometer (MRM) of Chang'e-1 and physical temperature (TP) data obtained from Diviner of Lunar Reconnaissance Orbiter (LRO). Here, permittivity mapping is not carried out above 60° latitudes towards the lunar poles due to large anomaly in the physical temperature obtained from the Diviner. Microwave frequencies, which are used to generate these maps are 3 GHz, 7.8 GHz, 19.35 GHz and 37 GHz. Permittivity values are simulated using TB values at these four frequencies. Here, weighted average of physical temperature obtained from Diviner are used to compute permittivity at each microwave frequencies. Longer wavelengths of microwave signals give information of more deeper layers of the lunar surface as compared to smaller wavelength. Initially, microwave emissivity is estimated using TB values from MRM and physical temperature (TP) from Diviner. From estimated emissivity the real part of permittivity (ε), is calculated using Fresnel equations. The permittivity maps of equatorial lunar surface is generated. The simulated permittivity values are normalized with respect to density for easy comparison of simulated permittivity values with the permittivity values of Apollo samples as well as with the permittivity values of Terrestrial Analogue of Lunar Soil (TALS) JSC-1A. Lower value of dielectric constant (ε‧) indicates that the corresponding lunar surface is smooth and doesn't have rough rocky terrain. Thus a future lunar astronaut can use these data to decide proper landing site for future lunar missions. The results of this paper will serve as input to future exploration of lunar surface.

Wireless power transfer based on dielectric resonators with colossal permittivity

NASA Astrophysics Data System (ADS)

Song, Mingzhao; Belov, Pavel; Kapitanova, Polina

2016-11-01

Magnetic resonant wireless power transfer system based on dielectric disk resonators made of colossal permittivity (ɛ = 1000) and low loss (tan δ = 2.5 × 10-4) microwave ceramic is experimentally investigated. The system operates at the magnetic dipole mode excited in the resonators providing maximal power transfer efficiency of 90% at the frequency 232 MHz. By applying an impedance matching technique, the efficiency of 50% is achieved within the separation between the resonators d = 16 cm (3.8 radii of the resonator). The separation, misalignment and rotation dependencies of wireless power transfer efficiency are experimentally studied.

Magneto-tunable relaxor ferroelectric properties in tricolor superlattices

NASA Astrophysics Data System (ADS)

Lee, Dongwook; Ah Qune, L. F. N.; Seo, Ji Won

2018-05-01

An artificial structure composed of antiferroelectric NdMnO3, SrMnO3, and LaMnO3 layers exhibits high dielectric permittivity. It also shows ferromagnetic behavior despite that the layers are all antiferromagnetic. The structure displays frequency-dependent relaxor behavior under AC electric field and the permittivity increased up to 70% by an external magnetic field. Inhomogeneous polar nano-regions occur at the interfaces inside the structure and it originates from Mn3+/Mn4+, which induces ferroelectric/ferromagnetic properties in the structure and causes ferroelectric relaxor as well as magnetic-field induced behavior.

Complex permeability and permittivity spectra of percolated Fe50Co50/Cu granular composites

NASA Astrophysics Data System (ADS)

Massango, Herieta; Tsutaoka, Takanori; Kasagi, Teruhiro; Yamamoto, Shinichiro; Hatakeyama, Kenichi

2017-11-01

Complex permeability and permittivity spectra of Fe50Co50/Cu hybrid granular composite materials have been studied in the RF to microwave frequency range. At low Cu particle content, the Fe50Co50/Cu hybrid sample shows a metallic percolative property with the electrical conductivity value about 0.1 S/cm. However, the low frequency plasmonic (LFP) state with negative permittivity (ENG) spectrum was not observed. An abrupt increase of electrical conductivity takes place at 14 to 16 vol% Cu content where the conductivity becomes above 1.0 S/cm; the Fe50Co50/Cu composite possesses the LFP state with negative permittivity spectrum below a characteristic frequency. The complex permittivity spectra in the LFP state can be described by the Drude model. Magnetic permeability spectrum in the LFP state showed a broad frequency dispersion above 10 MHz; a small negative permeability (MNG) dispersion was observed from 2 to 10 GHz. Consequently, the double negative (DNG) electromagnetic property with MNG and ENG was realized in the microwave range for the Cu content of 26 and 30 vol%.

Biofilm monitoring using complex permittivity.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Altman, Susan Jeanne; McGrath, Lucas K.; Dolan, Patricia L.

2008-10-01

There is strong interest in the detection and monitoring of bio-fouling. Bio-fouling problems are common in numerous water treatments systems, medical and dental apparatus and food processing equipment. Current bio-fouling control protocols are time consuming and costly. New early detection techniques to monitor bio-forming contaminates are means to enhanced efficiency. Understanding the unique dielectric properties of biofilm development, colony forming bacteria and nutrient background will provide a basis to the effectiveness of controlling or preventing biofilm growth. Dielectric spectroscopy measurements provide values of complex permittivity, {var_epsilon}*, of biofilm formation by applying a weak alternating electric field at various frequencies. Themore » dielectric characteristic of the biofilm, {var_epsilon}{prime}, is the real component of {var_epsilon}* and measures the biofilm's unique ability to store energy. Graphically observed dependencies of {var_epsilon}{prime} to frequency indicate dielectric relaxation or dielectric dispersion behaviors that mark the particular stage of progression during the development of biofilms. In contrast, any frequency dependency of the imaginary component, {var_epsilon}{double_prime} the loss factor, is expressed as dielectric losses from the biofilm due to dipole relaxation. The tangent angle of these two component vectors is the ratio of the imaginary component to the real component, {var_epsilon}{double_prime}/{var_epsilon}{prime} and is referred to as the loss angle tangent (tan {delta}) or dielectric loss. Changes in tan {delta} are characteristic of changes in dielectric losses during various developmental stages of the films. Permittivity scans in the above figure are of biofilm growth from P. Fluorescens (10e7 CFU's at the start). Three trends are apparent from these scans, the first being a small drop in the imaginary permittivity over a 7 hours period, best seen in the Cole-Cole plot (a). The second trend is observed two hours after inoculation when the permittivity begins to increase slightly over the next 20 hours, best seen in the shift from 1000 Hz to 5000 Hz in tan {delta} at the high frequencies (c). Because of similar dielectric relaxation properties noted by the comparable size of the semicircles, plot (a), and the height of tan {delta}, plot (c), within the first 29 hours, cell activity levels did not appreciably change. The third trend is observed when the complex permittivity value drops by orders of magnitude between 29 hours and 37 hours, best seen in the log [E] plot (b), and in the drop of the dielectric loss, tan {delta}, to 0. This change in the dielectric properties in the bio environment is nearly independent of all frequencies (c) and dissimilar from the original condition when only bacteria and nutrient was present in the biofilm chambers. The semicircles in plot (a) for this period decreased below the resolution of the graph, implying a large difference in the dielectric behavior of the cells/biofilms consisting of low dielectric losses. We believe these large changes are related to the on-set of biofilms.« less

The Importance of the Solids Loading on Confirming the Dielectric Nanosize Dependence of BaTiO3 Powders by Slurry Method

PubMed Central

Zhou, Wei; Nie, Yi Mei; Li, Shu Jing; Liang, Hai Yan

2013-01-01

The dielectric nanosize dependence of BaTiO3 powders was investigated by the slurry method, where two series of BaTiO3 slurries with 10 vol% and 30 vol% solids loadings were prepared as model samples. Applying the Bruggeman-Hanai equation, the high-frequency limiting permittivity (ε h) of the slurries was extracted from the dielectric spectra. The ε h of the 10 vol% slurry showed abnormal size independence in the range from 100 nm to 700 nm, and the ε h of the 30 vol% slurry exhibited good agreement with the previous prediction. Through analysing quantitatively the response of ε h to the changing permittivity of the powders under different solids loading, it was found that the ε h of the slurry with lower solids loading is more inclined to be interfered by the systematic and random errors. Furthermore, a high permittivity value was found in the BaTiO3 powders with 50 nm particle size. PMID:23844376

Fluid and microfluidic dielectric measurement using a cavity perturbation method at microwave C-band

NASA Astrophysics Data System (ADS)

Asghari, Aref

The utilization of cavity perturbation technique in dielectric property measurement of fluid and micro-fluid is investigated in this thesis to better assist the ever-growing needs of science and technology for analysis and characterization of such materials in various applications from genetics, MEMS devices, to consumer product industry. Development of different techniques for measuring complex dielectric properties of fluid and micro-fluids at Giga (10 9)-Hz frequencies is of significant importance as their usage is increasingly coupled with infrared and microwave electromagnetic wavelengths. Conventional cavity perturbation method could provide a sensitive and convenient system for measuring fluids of low (e.g., epsilonr <10) permittivity that meets the assumptions of negligible perturbation to the electromagnetic field distribution in the cavity. Developing a methodology that uses conventional cavity perturbation method that is however suitable for a sensitive, accurate, and reliable measurement of high permittivity polar liquids at microwave C-band is the goal in the current work. Systematic studies are carried out, using de-ionic (DI) water as test specimens, to evaluate the influence of sample's container, volume, dimension, and temperature on the sensitivity and reliability of microwave dielectric measurement. The cavity perturbation measurement of DI water in a 1 mm diameter capillary tube showed well-defined temperature dependence of dielectric permittivity and loss coefficients of water. Observation of a permittivity peak in temperature range tested at 4GHz around -10 °C implies an important relaxation in low temperatures at microwave C-band, which corresponds to a critical slowing down of polarization reorientation in crystallized (icy) H2O. Numerical simulations using Finite Element Analysis (FEA) COMSOL suites were conducted to established the optimum amount of liquid water for cavity perturbation testing at microwave C-band (in perfectly conducting condition). The results showed at TE103 mode the tube D4= 4mm diameter (272 muL liquid volume capacity) provides the best measurement sensitivity in terms of resonant shift and low loss while for TE105 the 2mm 68 (muL liquid volume capacity) tube is the most promising. The experimental results yielded a shape factor of around 2 and 1 for epsilon' and epsilon", respectively. The examination of epsilon' and epsilon" interdependence using Kramers-Kronig concept showed the permittivity loss values is 4 times more dependent to the quality factor of resonant peak than permittivity. On the other hand, the dielectric permittivity dependence to resonant frequency was calculated around 2 times bigger than dielectric loss which signifies the importance of epsilon" in high loss liquid measurement by the cavity resonant perturbation method.

Strong interfacial polarization in graphene/ZnO nanocomposite for high-performance miniscule permittivity materials

NASA Astrophysics Data System (ADS)

Shoeb, Mohd; Mobin, Mohammad; Naqvi, Alim H.

2018-05-01

In the 21st century evolution of microelectronics industries, consumptions of integrated circuits (IC's) increases, so the demand of miniscule permittivity (MP) material with minimum loss factor arises in the electronics industries. Graphene embedded ZnO Nanoparticle (Gr/ZnO NCs) is synthesized and studied their dielectric properties In the studied frequency range 75 kHz to 7 MHz. In the sample Gr/ZnO NCs dielectric permittivity decrease gradually from 7.2 to 6.7 as the frequency increases, whereas dielectric permittivity of ZnO NPs shows also diminishing behavior in the range 75 to 20 as the frequency increases. In the Gr/ZnO NCs, Maxwell-Wagner polarization model explains strong interfacial polarization to presence of functionalization group and lattice defects on graphene sheet.

Unusual polarity-dependent patterns in a bent-core nematic liquid crystal under low-frequency ac field.

PubMed

Xiang, Ying; Zhou, Meng-jie; Xu, Ming-Ya; Salamon, Péter; Éber, Nándor; Buka, Ágnes

2015-04-01

Electric-field-induced patterns of diverse morphology have been observed over a wide frequency range in a recently synthesized bent-core nematic (BCN) liquid crystal. At low frequencies (up to ∼25 Hz), the BCN exhibited unusual polarity-dependent patterns. When the amplitude of the ac field was enhanced, these two time-asymmetrical patterns turned into time-symmetrical prewavylike stripes. At ac frequencies in the middle-frequency range (∼50-3000 Hz), zigzag patterns were detected whose obliqueness varied with the frequency. Finally, if the frequency was increased above 3 kHz, the zigzag pattern was replaced by another, prewavylike pattern, whose threshold voltage depended on the frequency; however, the wave vector did not. For a more complete characterization, material parameters such as elastic constants, dielectric permittivities, and the anisotropy of the diamagnetic susceptibility were also determined.

Impact of Magneto-Electric Materials and Devices on Tactical Radio (and Radar)

DTIC Science & Technology

2007-04-01

and frequency dependent variable permittivity in a single device • Magnetic properties controlled by electric field. The goals of the seedling...such as HoMnO3) and composites (such as PZT- Terfenol-D). Other possible candidate materials are thought to include colossal magnetoresistive oxides

High microwave attenuation performance of planar carbonyl iron particles with orientation of shape anisotropy field

NASA Astrophysics Data System (ADS)

Guo, Cheng; Yang, Zhihong; Shen, Shile; Liang, Juan; Xu, Guoyue

2018-05-01

Planar anisotropy carbonyl iron (PACI) particles were prepared from commercial spherical carbonyl iron particles through a high performance ball-milling technique. The paraffin composites with orientation of shape anisotropy field for these PACI particles were obtained by applying an external magnetic field during the fabrication process. The frequency-dependent complex permeability values of these prepared paraffin composites have been investigated in the frequency range of 1-18 GHz. The results demonstrate that the orientation of shape anisotropy field for these PACI particles can effectively increase the complex permeability and decrease the complex permittivity values. Benefit from the enhancement in the complex permeability and reduction in the complex permittivity, the better impedance matching condition can be obtained and thus the good microwave absorption performance can be achieved for the samples with enough magnetic field orientation time.

Experimental Procedure for Determination of the Dielectric Properties of Biological Samples in the 2-50 GHz Range

PubMed Central

Odelstad, Elias; Raman, Sujith; Rydberg, Anders

2014-01-01

The objective of this paper was to test and evaluate an experimental procedure for providing data on the complex permittivity of different cell lines in the 2–50-GHz range at room temperature, for the purpose of future dosimetric studies. The complex permittivity measurements were performed on cells suspended in culture medium using an open-ended coaxial probe. Maxwell’s mixture equation then allows the calculation of the permittivity profiles of the cells from the difference in permittivity between the cell suspensions and pure culture medium. The open-ended coaxial probe turned out to be very sensitive to disturbances affecting the measurements, resulting in poor precision. Permittivity differences were not large in relation to the spread of the measurements and repeated measurements were performed to improve statistics. The 95% confidence intervals were computed for the arithmetic means of the measured permittivity differences in order to test the statistical significance. The results showed that for bone cells at the lowest tested concentration (33 500/ml), there were significance in the real part of the permittivity at frequencies above 30 GHz, and no significance in the imaginary part. For the second lowest concentration (67 000/ml) there was no significance at all. For a medium concentration of bone cells (135 000/ml) there was no significance in the real part, but there was significance in the imaginary part at frequencies below about 25 GHz. The cell suspension with a concentration of 1 350 000/ml had significance in the real part for both high (above 30 GHz) and low (below 15 GHz) frequencies. The imaginary part showed significance for frequencies below 25 GHz. In the case of an osteosarcoma cell line with a concentration of 2 700 000/ml, only the imaginary part showed significance, and only for frequencies below 15 GHz. For muscle cells at a concentration of 743 450/ml, there was only significance in the imaginary part for frequencies below 5 GHz. The experimental data indicated that the complex permittivity of the culture medium may be used for modeling of cell suspensions. PMID:27170886

Theoretical investigation of resonance frequencies in long wavelength electromagnetic wave scattering process from plasma prolate and oblate spheroids placed in a dielectric layer

NASA Astrophysics Data System (ADS)

Ahmadizadeh, Y.; Jazi, B.; Abdoli-Arani, A.

2014-01-01

Response of a prolate spheroid plasma and/or an oblate spheroid plasma in presence of long wavelength electromagnetic wave has been studied. The resonance frequencies of these objects are obtained and it is found that they reduce to the resonance frequency of spherical cold plasma. Moreover, the resonant frequencies of prolate spheroid plasma and oblate spheroid plasma covered by a dielectric are investigated as well. Furthermore, their dependency on dielectric permittivity and geometry dimensions is simulated.

Anomalous nonlinear absorption in epsilon-near-zero materials: optical limiting and all-optical control.

PubMed

Vincenti, M A; de Ceglia, D; Scalora, Michael

2016-08-01

We investigate nonlinear absorption in films of epsilon-near-zero materials. The combination of large local electric fields at the fundamental frequency and material losses at the harmonic frequencies induce unusual intensity-dependent phenomena. We predict that the second-order nonlinearity of a low-damping, epsilon-near-zero slab produces an optical limiting effect that mimics a two-photon absorption process. Anomalous absorption profiles that depend on low permittivity values at the pump frequency are also predicted for third-order nonlinearities. These findings suggest new opportunities for all-optical light control and novel ways to design reconfigurable and tunable nonlinear devices.

AC conductivity and dielectric behavior of bulk Furfurylidenemalononitrile

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Ali, H. A. M.

2012-06-01

AC conductivity and dielectric behavior for bulk Furfurylidenemalononitrile have been studied over a temperature range (293-333 K) and frequency range (50-5×106 Hz). The frequency dependence of ac conductivity, σac, has been investigated by the universal power law, σac(ω)=Aωs. The variation of the frequency exponent (s) with temperature was analyzed in terms of different conduction mechanisms, and it was found that the correlated barrier hopping (CBH) model is the predominant conduction mechanism. The temperature dependence of σac(ω) showed a linear increase with the increase in temperature at different frequencies. The ac activation energy was determined at different frequencies. Dielectric data were analyzed using complex permittivity and complex electric modulus for bulk Furfurylidenemalononitrile at various temperatures.

Non-Debye relaxation and resonance phenomena in dielectric spectra of CaCu3Ti4O12 family functional ceramic materials

NASA Astrophysics Data System (ADS)

Turik, A. V.; Bogatin, A. S.

2015-01-01

Experimental data on dielectric spectra of calcium copper titanate, CaCu3Ti4O12 (CCTO) family functional ceramics have been studied and analyzed. It is shown that there are both non-Debye relaxation and resonance regions in their spectra. An occurrence of a retardation of complex permittivity and a relaxation of electric modulus is established. An average relaxation frequency of the electric modulus is considerably (in some cases several orders of magnitude) larger than the retardation frequency of the permittivity. A parallel connection of the capacity and complex conductivity is used to model and interpret experimental data on a negative permittivity in the infralow frequency range. Computer simulation enables us to reveal that the hopping conductivity, characteristic for disordered heterogeneous systems, is to be taken into account to describe adequately experimental data on passing the real part of the capacity (or permittivity) through zero. We have found a critical frequency at which the parallel resonance would take place.

Measurements in Vacuum of the Complex Permittivity of Planetary Regolith Analog Materials in Support of the OSIRIS-REx Mission

NASA Astrophysics Data System (ADS)

Boivin, A.; Hickson, D. C.; Cunje, A.; Tsai, C. A.; Ghent, R. R.; Daly, M. G.

2017-12-01

In preparation for the OSIRIS-REx sample return mission, ground based radar data have been used to help characterize the carbonaceous asteroid (101955) Bennu as well as to produce a 3-D shape model. Radar data have also been used to derive the near-surface bulk density of the asteroid, a key engineering factor for sample acquisition and return. The relationship between radar albedo and bulk density of the nearsurface depends on the relative permittivity of the material, in this case regolith. The relative permittivity is complex such that ɛ r = ɛ r' + i ɛ r'', where ɛ r' is the dielectric constant and ɛ r'' is the loss factor. Laboratory permittivity measurements have been made in the past on a myriad of samples including Earth materials, lunar Apollo and analog samples, Mars soil analog samples, some meteorites, and cometary analog samples in support of the Rosetta mission. These measurements have been made in different frequency bands and in various conditions; however, no measurements to date have systematically explored the effect of changes in mineralogy on the complex permittivity, and particularly the loss tangent (tanδ , the ratio of ɛ r'' to ɛ r'). The loss tangent controls the absorption of the signal by the material. Continuing our investigation of the effects of mineralogy on these properties, we will present for the first time results of complex permittivity measurements of the UCF/DSI-CI-2 CI asteroid regolith simulant produced by Deep Space Industries Inc. The simulant is mineralogically similar to the CI meteorite Orgueil. CI meteorites are the most spectrally similar meteorites to (101955) Bennu. Since the simulant has been provided to us un-mixed, several sub-samples will be created containing different amounts of carbon, thus allowing us to systematically investigate the effects of carbon content on the permittivity. In order to remove moisture from our samples, powders are baked at 250°C for 48hrs prior to being loaded into a coaxial transmission line and measured under vacuum. Measurements are made using a sweep of frequencies from 300 KHz to 8.5 GHz.

Electrical Conduction of Ba(Ti0.99Fe0.01)O3-δ Ceramic at High Temperatures

NASA Astrophysics Data System (ADS)

Yu, Zi-De; Chen, Xiao-Ming

2018-03-01

BaTiO3 and Ba(Ti0.99Fe0.01)O3-δ ceramics with dense microstructure have been synthesized by a solid-state reaction method, and their electrical conduction investigated by broadband electrical impedance spectroscopy at frequencies from 0.05 Hz to 3 × 106 Hz and temperatures from 200°C to 400°C. Compared with BaTiO3, the real part of the permittivity and the phase-transition temperature of Ba(Ti0.99Fe0.01)O3-δ decreased. Relaxation peaks appeared in the curves of the imaginary part of the permittivity as a function of frequency. With increase in frequency, the peaks gradually shifted towards higher frequency and their height increased. Conductivity was closely related to frequency and temperature. Frequency-dependent conductivity was analyzed using the Jonscher double power law. Compared with BaTO3, Ba(Ti0.99Fe0.01)O3-δ exhibited high impedance at given frequency and temperature. Impedance Cole-Cole plots displayed two semicircles, which could be well fit using two parallel RC equivalent circuit models. The conductivity activation energy was found to be around 1 eV. For Ba(Ti0.99Fe0.01)O3-δ , the electrical modulus curve versus frequency displayed two peaks.

Electrical Conduction of Ba(Ti0.99Fe0.01)O3- δ Ceramic at High Temperatures

NASA Astrophysics Data System (ADS)

Yu, Zi-De; Chen, Xiao-Ming

2018-07-01

BaTiO3 and Ba(Ti0.99Fe0.01)O3- δ ceramics with dense microstructure have been synthesized by a solid-state reaction method, and their electrical conduction investigated by broadband electrical impedance spectroscopy at frequencies from 0.05 Hz to 3 × 106 Hz and temperatures from 200°C to 400°C. Compared with BaTiO3, the real part of the permittivity and the phase-transition temperature of Ba(Ti0.99Fe0.01)O3- δ decreased. Relaxation peaks appeared in the curves of the imaginary part of the permittivity as a function of frequency. With increase in frequency, the peaks gradually shifted towards higher frequency and their height increased. Conductivity was closely related to frequency and temperature. Frequency-dependent conductivity was analyzed using the Jonscher double power law. Compared with BaTO3, Ba(Ti0.99Fe0.01)O3- δ exhibited high impedance at given frequency and temperature. Impedance Cole-Cole plots displayed two semicircles, which could be well fit using two parallel RC equivalent circuit models. The conductivity activation energy was found to be around 1 eV. For Ba(Ti0.99Fe0.01)O3- δ , the electrical modulus curve versus frequency displayed two peaks.

Determination of the magnetoelectric coupling coefficient from temperature dependences of the dielectric permittivity for multiferroic ceramics Bi{sub 5}Ti{sub 3}FeO{sub 15}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartkowska, J. A., E-mail: joanna.bartkowska@us.edu.pl; Dercz, J.

2013-11-15

In the multiferroic materials, the dielectric and magnetic properties are closely correlated through the coupling interaction between the ferroelectric and magnetic order. We attempted to determine the magnetoelectric coupling coefficient from the temperature dependences of the dielectric permittivity for multiferroic Bi{sub 5}Ti{sub 3}FeO{sub 15}. Multiferroic ceramics Bi{sub 5}Ti{sub 3}FeO{sub 15} belong to materials of the Aurivillius-type structure. Multiferroic ceramics Bi{sub 5}Ti{sub 3}FeO{sub 15} was synthesized via sintering the Bi{sub 2}O{sub 3} and Fe{sub 2}O{sub 3} mixture and TiO{sub 2} oxides. The precursor material was ground in a high-energy attritorial mill for 5 hours. This material was obtained by a solid-statemore » reaction process at T = 1313 K. We investigated the temperature dependences of the dielectric permittivity for the different frequencies. From the dielectric measurements, we determined the temperature of phase transition of the ferroelectric-to-paraelectric type at about 1013 K. Based on dielectric measurements and theoretical considerations, the values of the magnetoelectric coupling coefficient were specified.« less

Defect Complex Effect in Nb Doped TiO2 Ceramics with Colossal Permittivity

NASA Astrophysics Data System (ADS)

Li, Fuchao; Shang, Baoqiang; Liang, Pengfei; Wei, Lingling; Yang, Zupei

2016-10-01

Donor-doped Nb x Ti1- x O2 ( x = 1%, 2%, 4%, 6%, and 8%) ceramics with giant permittivity (>104) and a very low dielectric loss (˜0.05) were sintered under flowing N2 at 1400°C for 10 h. By increasing Nb doping concentration, two different dielectric responses were evidenced in the frequency dependence of dielectric properties of Nb doped TiO2 ceramics, which corresponded to the space charge polarization and the electron-pinned defect-dipoles effect, respectively. Especially, combined with the x-ray photoelectron spectroscopy results, the electron-pinned defect-dipoles induced by the 2({Nb}^{5 + } )_{{Ti}}^{ bullet } to 4({Ti}^{3 + } )^'_{{Ti}} leftarrow {V}_{{o}}^{ bullet bullet } defect complex were further confirmed to give rise to both their high ɛr and low tan δ in the high frequency range for the Nb x Ti1- x O2 ceramics with x > 4%.

Dielectric properties of binary mixtures of methyl iso butyl ketone and amino silicone oil

NASA Astrophysics Data System (ADS)

Shah, K. N.; Rana, V. A.; Trivedi, C. M.; Vankar, H. P.

2017-05-01

Dielectric permittivity ɛ*(ω) = ɛ' - jɛ″ of the binary mixtures of the methyl iso butyl ketone and amino silicone oil in the frequency range 100 Hz to 2 MHz were measured using precision LCR meter at 305.15 K. Relative complex permittivity spectra in the frequency range 100 Hz to 2 MHz, of the mixture solutions of varying concentrations is reported. Determined values of the permittivity at optical frequency of all the samples are also reported. The dielectric parameters are used to gain information about the effect of concentration variation of components of the mixtures on the dielectric properties. It also provides the information about electrode polarization phenomena taking place under the low frequency A.C. electric field.

Development of a new medium frequency EM device: Mapping soil water content variations using electrical conductivity and dielectric permittivity

NASA Astrophysics Data System (ADS)

Kessouri, P.; Buvat, S.; Tabbagh, A.

2012-12-01

Both electrical conductivity and dielectric permittivity of soil are influenced by its water content. Dielectric permittivity is usually measured in the high frequency range, using GPR or TDR, where the sensitivity to water content is high. However, its evaluation is limited by a low investigation depth, especially for clay rich soils. Electrical conductivity is closely related not only to soil water content, but also to clay content and soil structure. A simultaneous estimation of these electrical parameters can allow the mapping of soil water content variations for an investigation depth close to 1m. In order to estimate simultaneously both soil electrical conductivity and dielectric permittivity, an electromagnetic device working in the medium frequency range (between 100 kHz and 10 MHz) has been designed. We adopted Slingram geometry for the EM prototype: its PERP configuration (vertical transmission loop Tx and horizontal measuring loop Rx) was defined using 1D ground models. As the required investigation depth is around 1m, the coil spacing was fixed to 1.2m. This prototype works in a frequency range between 1 and 5 MHz. After calibration, we tested the response of prototype to objects with known properties. The first in situ measurements were led on experimental sites with different types of soils and different water content variations (artificially created or natural): sandy alluvium on a plot of INRA (French National Institute for Agricultural Research) in Orléans (Centre, France), a clay-loam soil on an experimental site in Estrée-Mons (Picardie, France) and fractured limestone at the vicinity of Grand (Vosges, France). In the case of the sandy alluvium, the values of dielectric permittivity measured are close to those of HF permittivity and allow the use of existing theoretical models to determine the soil water content. For soils containing higher amount of clay, the coupled information brought by the electrical conductivity and the dielectric permittivity is used. Variations of water content detected by the EM prototype are confirmed by additional DC electrical profiling and direct mass water content measurements along depth. For the clay-loam soil, containing more than 20% of clay, the relative dielectric permittivity values, ranging from 63 to 138, are much higher than those expected in the high frequency range (above 20 MHz, the highest measured permittivity is equal to 81 for water). In the medium frequency range, those values are very likely due to interfacial polarization. This effect, also known as Maxwell-Wagner polarization, should increase with the soil clay content. The first measuring trial is coherent with the gravimetric water content as well as DC electrical profiling measurements. For a clay rich soil, the EM prototype is able to detect water content variations for an investigation depth close to 1m with both electrical conductivity and dielectric permittivity in the medium frequency range. Other field experiments are scheduled to confirm these results on other types of soils.

Study of the low-frequency dispersion of permittivity and resistivity in tight rocks

NASA Astrophysics Data System (ADS)

Liu, Hongqi; Jie, Tian; Li, Bo; Youming, Deng; Chunning, Qiu

2017-08-01

The road to understanding the frequency dispersion (relaxation) of permittivity and resistivity in tight rocks remains relatively uncharted. Our team from Da'anzhai Group, Jurassic formation, Sichuan Basin carried out practical research to explore this phenomenon. The research was conducted under laboratory conditions for a selection of low frequencies, with ranges between 0.1 Hz to 1 kHz. Our research has shown that, although both the permittivity and resistivity decrease as the frequency increases, the two individual metrics display different behaviours when compared with each other. While the degree of resistivity variation is minimal, to the point that it is redundant, the permittivity, on the other hand, demonstrates something that is scientifically noteworthy. Permittivity has a distinctive dispersion degree across the entire sample of frequencies and the difference between the minimum and maximum frequencies is several orders of magnitude. An additional, and unexpected, learning from our research is that the level of frequency dispersion increases as the water saturation and concentration increases. In this paper, a collection of equations has been formulated to describe this relationship. These equations particularly shed light on the areas of rock porosity and saturation. They also show that the degree of frequency dispersion of permittivity or resistivity can be used as a function of water saturation and concentration. Two new variables are introduced here, DR and DC, to demonstrate the relaxation law quantitatively. In our practical research, we have characterised the relationship between the saturation and concentration with dielectric relaxation, using three different concentrations of DR and DC and five different saturations of NaCl solution. In difference to conventional Archie's multiple experimental parameters, we have established a new formula to derive the saturation from Rp and Cp, or from DR and DC directly. Two important frequencies were also further investigated for Cp dispersion: first is the critical frequency, which marks the dispersion speed change from steep phase to steady phase, and second is the zero-frequency, which marks the dispersion when it approaches zero. All tight rocks were measured under the same conditions, with the results displaying the same pattern of variations. The results have led us to believe that Cp's frequency dispersion at low-frequencies provides a new methodology to characterise tight rocks.

Characterization of the relationship of the cure cycle chemistry to cure cycle processing properties

NASA Technical Reports Server (NTRS)

Kranbuehl, D. E.

1985-01-01

Dynamic dielectric analysis (DDA) is used to study curing polymer systems and thermoplastics. Measurements are made over a frequency range of six decades. This wide range of frequencies increases the amount of information which can be obtained. The data is analyzed in terms of the frequency dependence of the complex permittivity epsilon sup *, specific conductivity sigma (ohm/cm) and the relaxation time tau, parameters which are characteristic of the cure state of the material and independent of the size of the sample.

Macroscopic Models of Local Field Potentials and the Apparent 1/f Noise in Brain Activity

PubMed Central

Bédard, Claude; Destexhe, Alain

2009-01-01

The power spectrum of local field potentials (LFPs) has been reported to scale as the inverse of the frequency, but the origin of this 1/f noise is at present unclear. Macroscopic measurements in cortical tissue demonstrated that electric conductivity (as well as permittivity) is frequency-dependent, while other measurements failed to evidence any dependence on frequency. In this article, we propose a model of the genesis of LFPs that accounts for the above data and contradictions. Starting from first principles (Maxwell equations), we introduce a macroscopic formalism in which macroscopic measurements are naturally incorporated, and also examine different physical causes for the frequency dependence. We suggest that ionic diffusion primes over electric field effects, and is responsible for the frequency dependence. This explains the contradictory observations, and also reproduces the 1/f power spectral structure of LFPs, as well as more complex frequency scaling. Finally, we suggest a measurement method to reveal the frequency dependence of current propagation in biological tissue, and which could be used to directly test the predictions of this formalism. PMID:19348744

Magnetically tunable liquid dielectric with giant dielectric permittivity based on core-shell superparamagnetic iron oxide.

PubMed

Vinayasree, S; Nitha, T S; Tiwary, C S; Ajayan, P M; Joy, P A; Anantharaman, M R

2018-06-29

A liquid dielectric based on a core-shell architecture having a superparamagnetic iron oxide core and a shell of silicon dioxide was synthesized. The frequency dependence of dielectric properties was evaluated for different concentrations of iron oxide. The dependence of magnetic field on the dielectric properties was also studied. Aqueous ferrofluid exhibited a giant dielectric constant of 6.4 × 10 5 at 0.1 MHz at a concentration of 0.2 vol% and the loss tangent was 3. The large rise in dielectric constant at room temperature is modelled and explained using percolation theory and Maxwell-Wagner-Sillars type polarization. The ferrofluid is presumed to consist of nanocapacitor networks which are wired in series along the lateral direction and parallel along longitudinal direction. On the application of an external magnetic field, the chain formation and its alignment results in the variation of dielectric permittivity.

Enhancement of polar phase and conductivity relaxation in PIL-modified GO/PVDF composites

NASA Astrophysics Data System (ADS)

Xu, Pei; Fu, Weijia; Cui, Zhaopei; Ding, Yunsheng

2018-02-01

To investigate the effect of graphene oxide (GO) modified by polymerized ionic liquid (PIL) on the crystallization and dielectric relaxation of poly(vinylidene fluoride) (PVDF), a series of PVDF composites have been prepared using the solution casting method. The ion-dipole interaction between PIL and >CF2 and the π-dipole interaction between GO and >CF2 can induce synergistically the polar phase, and the π-ion interaction between GO and PIL can strengthen the induction effect of the polar phase and decrease the degree of crystallization of PVDF. The electric modulus and conductivity relaxation are employed to analyze the experimental complex dielectric permittivity. In the frequency spectra of complex permittivity of PVDF composites, space charge polarization and conductivity lead to a large value of dielectric permittivity. The temperature dependence of relaxation time of conductivity relaxation accords with the Arrhenius equation. A low degree of crystallization, more ion concentration, and polar phase in PVDF/PIL/GO enhance the movement of the polymer chain segment and charge carriers.

Numerical band structure calculations of plasma metamaterials

NASA Astrophysics Data System (ADS)

Pederson, Dylan; Kourtzanidis, Konstantinos; Raja, Laxminarayan

2015-09-01

Metamaterials (MM) are materials engineered to display negative macroscopic permittivity and permeability. These materials allow for designed control over electromagnetic energy flow, especially at frequencies where natural materials do not interact. Plasmas have recently found application in MM as a negative permittivity component. The permittivity of a plasma depends on its electron density, which can be controlled by an applied field. This means that plasmas can be used in MM to actively control the transmission or reflection of incident waves. This work focuses on a plasma MM geometry in which microplasmas are generated in perforations in a metal plate. We characterizethis material by its band structure, which describes its interaction with incident waves. The plasma-EM interactions are obtained by coupling Maxwell's equations to a simplified plasma momentum equation. A plasma density profile is prescribed, and its effect on the band structure is investigated. The band structure calculations are typically done for static structures, whereas our current density responds to the incident waves. The resulting band structures are compared with experimental results.

High-performance colossal permittivity materials of (Nb + Er) co-doped TiO2 for large capacitors and high-energy-density storage devices.

PubMed

Tse, Mei-Yan; Wei, Xianhua; Hao, Jianhua

2016-09-21

The search for colossal permittivity (CP) materials is imperative because of their potential for promising applications in the areas of device miniaturization and energy storage. High-performance CP materials require high dielectric permittivity, low dielectric loss and relatively weak dependence of frequency- and temperature. In this work, we first investigate the CP behavior of rutile TiO2 ceramics co-doped with niobium and erbium, i.e., (Er0.5Nb0.5)xTi1-xO2. Excellent dielectric properties were observed in the materials, including a CP of up to 10(4)-10(5) and a low dielectric loss (tan δ) down to 0.03, which are lower than that of the previously reported co-doped TiO2 CP materials when measured at 1 kHz. Stabilities of frequency and temperature were also accomplished via doping Er and Nb. Valence states of the elements in the material were analyzed using X-ray photoelectron spectroscopy. The Er induced secondary phases were observed using elemental mapping and energy-dispersive spectrometry. Consequently, this work may provide comprehensive guidance to develop high-performance CP materials for fully solid-state capacitor and energy storage applications.

Characterizing the Attenuation of Coaxial and Rectangular Microwave-Frequency Waveguides at Cryogenic Temperatures (Open Access, Publisher’s Version)

DTIC Science & Technology

2017-05-04

Wallraff *Correspondence: philipp.kurpiers@phys.ethz.ch Department of Physics, ETH Zürich, Zürich, CH-8093, Switzerland Abstract Low- loss waveguides...and single photon levels. More specifically, we characterize the frequency-dependent loss of a range of coaxial and rectangular microwave waveguides...down to 0.005 dB/m using a resonant-cavity technique. We study the loss tangent and relative permittivity of commonly used dielectric waveguide materials

Effect of a magnetic field on the permittivity of 80%La0.7Sr0.3MnO3/20%GeO2 composite

NASA Astrophysics Data System (ADS)

Kabirov, Yu. V.; Gavrilyachenko, V. G.; Bogatin, A. S.; Sitalo, E. I.; Yatsenko, V. K.

2018-01-01

The dielectric properties of a magnetoresistive conducting two-phase 80%La0.7Sr0.3MnO3/20%GeO2 (wt %) composite have been studied near the percolation threshold in magnetic fields from 0 to 15 kOe at frequencies of the measurement field from 5 kHz to 1 MHz. The samples have inductive impedances; i.e., their permittivities can be considered negative due to a high conductivity in this frequency range. The permittivity increases in magnitude in magnetic field, and the values of the magnetodielectric coefficient reach 23% at room temperature. The reasons for the effect of magnetic field on the dielectric permittivity of samples are discussed.

Temperature dependent dielectric behavior of sol-gel grown Y0.95Ca0.05MnO3/Si junction

NASA Astrophysics Data System (ADS)

Dhruv, Davit; Joshi, Zalak; Solanki, Sapana; Sagapariya, Khushal; Makwana, Pratima; Kansara, S. B.; Joshi, A. D.; Pandya, D. D.; Solanki, P. S.; Shah, N. A.

2017-05-01

We have successfully fabricated divalent doped Y0.95Ca0.05MnO3 film on (100) single crystalline n-type Si substrate by spin coating assisted chemical solution deposition technique. The X-ray diffraction (XRD) pattern of thin film depicts that the film has (h00) directional growth on substrate. Thin film possesses -1.4% compressive strain at the interface level and thin film thickness is found to be ˜ 78nm. Dielectric property of film has been studied by Agilent LCR meter from 100Hz to 2MHz applied field frequency at temperatures 150 to 300K. Real dielectric permittivity decreases and imaginary dielectric permittivity increases with increasing applied frequency. Furthermore, at low temperatures, higher dielectric is observed in all the frequency range studied and it decreases with increasing temperature due to thermal excitation induced increased charge carrier movements across the film lattice. The relaxation mechanism of Y0.95Ca0.05MnO3 film has been understood through cole-cole plots.

Dielectric relaxation studies of binary mixture of β-picoline and methanol using time domain reflectometry at different temperatures

NASA Astrophysics Data System (ADS)

Trivedi, C. M.; Rana, V. A.; Hudge, P. G.; Kumbharkhane, A. C.

2016-08-01

Complex permittivity spectra of binary mixtures of varying concentrations of β-picoline and Methanol (MeOH) have been obtained using time domain reflectometry (TDR) technique over frequency range 10 MHz to 25 GHz at 283.15, 288.15, 293.15 and 298.15 K temperatures. The dielectric relaxation parameters namely static permittivity (ɛ0), high frequency limit permittivity (ɛ∞1) and the relaxation time (τ) were determined by fitting complex permittivity data to the single Debye/Cole-Davidson model. Complex nonlinear least square (CNLS) fitting procedure was carried out using LEVMW software. The excess permittivity (ɛ0E) and the excess inverse relaxation time (1/τ)E which contain information regarding molecular structure and interaction between polar-polar liquids were also determined. From the experimental data, parameters such as effective Kirkwood correlation factor (geff), Bruggeman factor (fB) and some thermo dynamical parameters have been calculated. Excess parameters were fitted to the Redlich-Kister polynomial equation. The values of static permittivity and relaxation time increase nonlinearly with increase in the mol-fraction of MeOH at all temperatures. The values of excess static permittivity (ɛ0E) and the excess inverse relaxation time (1/τ)E are negative for the studied β-picoline — MeOH system at all temperatures.

Negative permittivity and permeability spectra of Cu/yttrium iron garnet hybrid granular composite materials in the microwave frequency range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsutaoka, Takanori, E-mail: tsutaok@hiroshima-u.ac.jp; Fukuyama, Koki; Kinoshita, Hideaki

2013-12-23

The relative complex permittivity and permeability spectra of the coagulated copper and yttrium iron garnet (Cu/YIG) hybrid granular composite materials have been studied in the microwave range. The insulator to metal transition was observed at the percolation threshold of Cu particle content (φ{sub Cu} = 16.0 vol. %) in the electrical conductivity. In the percolation threshold, the low frequency plasmonic state caused by the metallic Cu particle networks was observed. The percolated Cu/YIG granular composites show simultaneous negative permittivity and permeability spectra under external magnetic fields.

Extraction of dielectric and magnetic properties of carbonyl iron powder composites at high frequencies

NASA Astrophysics Data System (ADS)

Zivkovic, I.; Murk, A.

2012-06-01

In this paper, we examine carbonyl iron composites in silicone rubber and epoxy matrices. Transmission measurements were performed at W (70 to 110 GHz) and Ka (26 to 40 GHz) bands and effective permittivity and permeability of composites with 10% volume fraction of carbonyl iron powder (CIP) were extracted at these frequencies. To extract permittivity and permeability of carbonyl iron powder in W and Ka bands, we use Looyenga formula. We extract permittivity and permeability of CIP from both silicone rubber and epoxy based composites and good agreement is achieved.

Structural and dielectric properties of Ba{sub 2}LaSbO{sub 6} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumari, Premlata, E-mail: k.premlata1@gmail.com; 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 β =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 realmore » 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.« less

Low-frequency dynamic response of the bismuth strontium ferrite (Bi,Sr)FeO3- x

NASA Astrophysics Data System (ADS)

Pronin, A. A.; Torgashev, V. I.; Bush, A. A.; Gorshunov, B. P.; Volkov, A. A.; Prokhorov, A. S.

2009-03-01

Broad-range measurements of the dynamic response of polycrystalline samples of the (Bi,Sr)FeO3- x perovskite-like solid solution are performed over a frequency range from 10 Hz to 1 GHz at temperatures of 100-300 K for the first time. The colossal dielectric constant effect and the influence of electric contacts on the results of measurements are considered. It is shown that the frequency dependences of the permittivity and dynamic conductivity of (Bi,Sr)FeO3- x samples can be described within the universal dielectric response model.

Optical Properties of Al-Doped ZnO Films in the Infrared Region and Their Absorption Applications

NASA Astrophysics Data System (ADS)

Zheng, Hua; Zhang, Rong-Jun; Li, Da-Hai; Chen, Xin; Wang, Song-You; Zheng, Yu-Xiang; Li, Meng-Jiao; Hu, Zhi-Gao; Dai, Ning; Chen, Liang-Yao

2018-05-01

The optical properties of aluminum-doped zinc oxide (AZO) thin films were calculated rapidly and accurately by point-by-point analysis from spectroscopic ellipsometry (SE) data. It was demonstrated that there were two different physical mechanisms, i.e., the interfacial effect and crystallinity, for the thickness-dependent permittivity in the visible and infrared regions. In addition, there was a blue shift for the effective plasma frequency of AZO when the thickness increased, and the effective plasma frequency did not exist for AZO ultrathin films (< 25 nm) in the infrared region, which demonstrated that AZO ultrathin films could not be used as a negative index metamaterial. Based on detailed permittivity research, we designed a near-perfect absorber at 2-5 μm by etching AZO-ZnO alternative layers. The alternative layers matched the phase of reflected light, and the void cylinder arrays extended the high absorption range. Moreover, the AZO absorber demonstrated feasibility and applicability on different substrates.

Extrinsic origins of the apparent relaxorlike behavior in CaCu3Ti4O12 ceramics at high temperatures: A cautionary tale

NASA Astrophysics Data System (ADS)

Li, Ming; Sinclair, Derek C.; West, Anthony R.

2011-04-01

Although the origins of the high effective permittivity observed in CaCu3Ti4O12 (CCTO) ceramics and single crystals at ˜100-400 K have been resolved, the relaxorlike temperature- and frequency-dependence of permittivity obtained from fixed frequency capacitance measurements at higher temperatures reported in the literature remains unexplained, especially as CCTO adopts a centrosymmetric cubic crystal structure in the range of ˜35-1273 K. Impedance spectroscopy studies reveal that this type of relaxorlike behavior is an artifact induced mainly by a nonohmic sample-electrode contact impedance. In addition, an instrument-related parasitic series inductance and resistance effect modifies the measured capacitance values as the sample resistance decreases with increasing temperature. This can lead to an underestimation of the sample capacitance and, in extreme cases, to so-called `negative capacitance.' Such a relaxorlike artifact and negative capacitance behavior are not unique to CCTO and may be expected in other leaky dielectrics whose resistance is low.

Study of complex permittivity spectra of binary mixtures of 2-chloroaniline and methanol in frequency range 10 KHz to 2 MHz at different temperatures

NASA Astrophysics Data System (ADS)

Shah, N. S.; Vankar, H. P.; Rana, V. A.

2017-05-01

The complex relative dielectric function ɛ*(ω)=ɛ'-jɛ″ of the binary mixture of 2-chloroaniline(2-CA) and methanol (MeOH) were measured using precision LCR meter in the frequency range of 10 KHz to 2 MHz The measurements were carried out at eight different temperatures and five different concentrations of 2-CA and MeOH. The loss tangent peaks were observed in the studied frequency range for all the binary mixtures. From the loss tangent peaks electrode polarization relaxation time were evaluated. In the plot of real part of complex permittivity against frequency, at different temperatures for 2-CA (54.54%) + MeOH (45.45%) and 2-CA (27.27%) + MeOH (72.72%)and 100% MeOH systems permittivity inversion effect was observed.

Calculating Permittivity and Dielectric Loss Frequency Spectra for Aqueous Electrolyte Solutions

NASA Astrophysics Data System (ADS)

Odinaev, S.; Makhmadbegov, R. S.

2018-01-01

Analytic expressions for dielectric permittivity factor ɛ1(ω) and dielectric dissipation factor ɛ2(ω) of electrolyte solutions are obtained, based on the ratio between complex factors of dielectric permittivity and specific conductivity. The range of frequency dispersion of dynamic factors ɛ1(ω) and ɛ2(ω) for aqueous solutions of LiCl, NaCl, KCl, and CsCl is considered. Numerical calculations are performed for friction coefficients β a and β b ; relaxation times τ a , τ b , and τ ab ; and factors ɛ1(ω) and ɛ2(ω) in a wide range of variation for ρ; concentration c; temperature T; and frequencies ω. The resulting theoretically calculated ɛ1(ω) and ɛ2(ω) values and the Cole-Cole diagram are in quantitative agreement with experimental data.

Measurement of the complex permittivity of microbubbles using a cavity perturbation technique for contrast enhanced ultra-wideband breast cancer detection.

PubMed

Ogunlade, Olumide; Chen, Yifan; Kosmas, Panagiotis

2010-01-01

Measurements of the complex permittivity of various concentrations of microbubbles in ethylene glycol liquid phantom have been carried out. A cavity perturbation technique using custom rectangular waveguide cavities, which are sensitive to small changes in the permittivity of the perturber, has been employed. Three different frequencies within the ultra-wideband (UWB) frequency spectrum have been used for the experiments. The results show that the concentration of the air filled microbubbles required to achieve a dielectric contrast as little as 2% exceeds the recommended dosage used in clinical ultrasound applications, by more than two orders of magnitude.

Dielectric relaxation of gamma irradiated muscovite mica

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaur, Navjeet; Singh, Mohan, E-mail: mohansinghphysics@gmail.com; Singh, Lakhwant

2015-03-15

Highlights: • The present article reports the effect of gamma irradiation on the dielectric relaxation characteristics of muscovite mica. • Dielectric and electrical relaxations have been analyzed in the framework of dielectric permittivity, electric modulus and Cole–Cole formalisms. • The frequency dependent electrical conductivity has been rationalized using Johnsher’s universal power law. • The experimentally measured electric modulus and conductivity data have been fitted using Havriliak–Negami dielectric relaxation function. - Abstract: In the present research, the dielectric relaxation of gamma irradiated muscovite mica was studied in the frequency range of 0.1 Hz–10 MHz and temperature range of 653–853 K, usingmore » the dielectric permittivity, electric modulus and conductivity formalisms. The dielectric constants (ϵ′ and ϵ′′) are found to be high for gamma irradiated muscovite mica as compared to the pristine sample. The frequency dependence of the imaginary part of complex electric modulus (M′′) and dc conductivity data conforms Arrhenius law with single value of activation energy for pristine sample and two values of activation energy for gamma irradiated mica sample. The experimentally assessed electric modulus and conductivity information have been interpreted by the Havriliak–Negami dielectric relaxation explanation. Using the Cole–Cole framework, an analysis of real and imaginary characters of the electric modulus for pristine and gamma irradiated sample was executed which reflects the non-Debye relaxation mechanism.« less

Age dependence of dielectric properties of bovine brain and ocular tissues in the frequency range of 400 MHz to 18 GHz

NASA Astrophysics Data System (ADS)

Schmid, Gernot; Überbacher, Richard

2005-10-01

In order to identify possible age-dependent dielectric properties of brain and eye tissues in the frequency range of 400 MHz to 18 GHz, measurements on bovine grey and white matter as well as on cornea, lens (cortical) and the vitreous body were performed using a commercially available open-ended coaxial probe and a computer-controlled vector network analyser. Freshly excised tissues of 52 animals of two age groups (42 adult animals, i.e. 16-24 month old and 10 young animals, i.e. 4-6 month old calves) were examined within 8 min (brain tissue) and 15 min (eye tissue), respectively, of the animals' death. Tissue temperatures for the measurements were 32 ± 1 °C and 25 ± 1 °C for brain and eye tissues, respectively. Statistical analysis of the measured data revealed significant differences in the dielectric properties of white matter and cortical lens tissue between the adult and the young group. In the case of white matter the mean values of conductivity and permittivity of young tissue were 15%-22% and 12%-15%, respectively, higher compared to the adult tissue in the considered frequency range. Similarly, young cortical lens tissue was 25%-76% higher in conductivity and 27%-39% higher in permittivity than adult cortical lens tissue.

Fabrication of Organic Radar Absorbing Materials: A Report on the TIF Project

DTIC Science & Technology

2005-05-01

thickness, permittivity and permeability. The ability to measure the permittivity and permeability is an essential requirement for designing an optimised...absorber. And good optimisations codes are required in order to achieve the best possible absorber designs . In this report, the results from a...through measurement of their conductivity and permittivity at microwave frequencies. Methods were then developed for optimising the design of

Properties of barium strontium titanate at millimeter wave frequencies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osman, Nurul; Free, Charles

2015-04-24

The trend towards using higher millimetre-wave frequencies for communication systems has created a need for accurate characterization of materials to be used at these frequencies. Barium Strontium Titanate (BST) is a ferroelectric material whose permittivity is known to change as a function of applied electric field and have found varieties of application in electronic and communication field. In this work, new data on the properties of BST characterize using the free space technique at frequencies between 145 GHz and 155 GHz for both thick film and bulk samples are presented. The measurement data provided useful information on effective permittivity and loss tangentmore » for all the BST samples. Data on the material transmission, reflection properties as well as loss will also be presented. The outcome of the work shows through practical measurement, that BST has a high permittivity with moderate losses and the results also shows that BST has suitable properties to be used as RAM for high frequency application.« less

Simulation of the halite dielectric spectrum in the infrared region

NASA Astrophysics Data System (ADS)

Aryomin, I. E.

2013-07-01

In this paper, we consider the practical efficiency of an simulation of a real frequency characteristic of complex permittivity of a NaCl halite crystal observed in the frequency range of establishment of elastic ionic polarization processes. In computational experiments, use was made of a cybernetic equation of permittivity, as well as the classical, corpuscular, and originally modified models of the considered physical phenomena.

Anisotropy of electromagnetically induced left-handedness in atomic three-level media based upon bianisotropic polarizabilities and tensor character

NASA Astrophysics Data System (ADS)

Krowne, Clifford M.

2008-05-01

A three-level atomic system, configured as either a gaseous medium or a solid state material, with a driving field establishing a Rabi frequency of control, is tested by a probe field. The medium has bianisotropic microscopic polarizability and magnetizability, from which the permittivity and permeability tensors are derived. Non-isotropy and polarization dependence for left-handedness (negative index of refraction) is demonstrated through examination of tensor components in the detuning frequency spectrum. These results have important implications for use in optical or electronic devices.

Optical characteristics of the nanoparticle coupled to a quantum molecular aggregate

NASA Astrophysics Data System (ADS)

Ropakova, I. Yu.; Zvyagin, A. A.

2017-11-01

Optical characteristics of a single nanoparticle, coupled to the one-dimensional quantum molecular aggregate is studied. Depending on the values of the coupling of the particle and its own frequency, with respect to the own frequency of the aggregated molecules, and the strength of the aggregation, the dynamical relative permittivity of the nanoparticle manifests the contribution from the exciton band, or/and the ones from the local level(s) caused by the particle. The refractive index and the extinction coefficient of the nanoparticle is also calculated.

Variable-permittivity linear inverse problem for the H(sub z)-polarized case

NASA Technical Reports Server (NTRS)

Moghaddam, M.; Chew, W. C.

1993-01-01

The H(sub z)-polarized inverse problem has rarely been studied before due to the complicated way in which the unknown permittivity appears in the wave equation. This problem is equivalent to the acoustic inverse problem with variable density. We have recently reported the solution to the nonlinear variable-permittivity H(sub z)-polarized inverse problem using the Born iterative method. Here, the linear inverse problem is solved for permittivity (epsilon) and permeability (mu) using a different approach which is an extension of the basic ideas of diffraction tomography (DT). The key to solving this problem is to utilize frequency diversity to obtain the required independent measurements. The receivers are assumed to be in the far field of the object, and plane wave incidence is also assumed. It is assumed that the scatterer is weak, so that the Born approximation can be used to arrive at a relationship between the measured pressure field and two terms related to the spatial Fourier transform of the two unknowns, epsilon and mu. The term involving permeability corresponds to monopole scattering and that for permittivity to dipole scattering. Measurements at several frequencies are used and a least squares problem is solved to reconstruct epsilon and mu. It is observed that the low spatial frequencies in the spectra of epsilon and mu produce inaccuracies in the results. Hence, a regularization method is devised to remove this problem. Several results are shown. Low contrast objects for which the above analysis holds are used to show that good reconstructions are obtained for both permittivity and permeability after regularization is applied.

Studies on the microwave permittivity and electromagnetic wave absorption properties of Fe-based nano-composite flakes in different sizes

NASA Astrophysics Data System (ADS)

Wu, Yanhui; Han, Mangui; Liu, Tao; Deng, Longjiang

2015-07-01

The effective permittivity of composites containing Fe-Cu-Nb-Si-B nanocrystalline micro flakes has been studied within 0.5-10 GHz. Obvious differences in microwave permittivity have been observed for composites consisting of large flakes (size range: 23-111 μm, average thickness: 4.5 μm) and small flakes (size range: 3-21 μm, average thickness: 1.3 μm). Both the real part and imaginary part of permittivity of large flake composite are much larger than these small one in a given frequency. And faster decrease of permittivity with the increasing frequency can be observed for large flake composite than that of small one. These differences in permittivity spectra of different flakes have been explained from the perspective of interfacial polarization and ac conductivity. The assumption that more extensive ohmic contact interface between large flakes and matrix has been validated by the fittings and the calculated percolation threshold. Meanwhile, the permeability spectra of both composites also have been studied by Lorentzian dispersion law. The broadened spectra can be attributed to the distribution of magnetic anisotropy fields of two kinds of ferromagnetic phases in the particles. Finally, the composite containing the small flakes exhibits better electromagnetic wave absorption properties.

Dielectric relaxation related to single-ionized oxygen vacancies in (Pb{sub 1-x}La{sub x})(Zr{sub 0.90}Ti{sub 0.10}){sub 1-x/4}O{sub 3} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pelaiz-Barranco, A., E-mail: pelaiz@fisica.uh.cu; Guerra, J.D.S.

2010-09-15

The dielectric relaxation phenomenon has been studied in lanthanum modified lead zirconate titanate ceramics in the high temperature paraelectric phase. The high temperature dielectric response revealed an anomalous behavior, which is characterized by an increase of the real component of the dielectric permittivity with the increase of the temperature. At the same time, a similar behavior, with very high values, has been observed in the imaginary component of the dielectric permittivity, which can be associated with conduction effects related to the conductivity losses. The frequency and temperature behavior of the complex dielectric permittivity has been analyzed considering the semi-empirical complexmore » Cole-Cole equation. The activation energy value, obtained from the Arrhenius' dependence for the relaxation time, was found to decreases with the increase of the lanthanum concentration and has been associated with single-ionized oxygen vacancies. The short-range hopping of oxygen vacancies is discussed as the main cause of the dielectric relaxation.« less

Frequency Dependence of Low-Voltage Electrowetting Investigated by Impedance Spectroscopy.

PubMed

Li, Ying-Jia; Cahill, Brian P

2017-11-14

An electrowetting-on-dielectric (EWOD) electrode was developed that facilitates the use of low alternating voltages (≤5 V AC ). This allows online investigation of the frequency dependence of electrowetting by means of impedance spectroscopy. The EWOD electrode is based on a dielectric bilayer consisting of an anodic tantalum pentoxide (Ta 2 O 5 ) thin film (d = 59.35 nm) with a high relative permittivity (ε d = 26.3) and a self-assembled hydrophobic silane monolayer. The frequency dependence of electrowetting was studied using an aqueous μL-sized sessile droplet on the planar EWOD electrode in oil. Experiments using electrochemical impedance spectroscopy and optical imaging indicate the frequency dependence of all three variables in the Young-Lippmann equation: the voltage drop across the dielectric layers, capacitance per unit area, and contact angle under voltage. The electrowetting behavior induced by AC voltages is shown to be well described by the Young-Lippmann equation for AC applications below a frequency threshold. Moreover, the dielectric layers act as a capacitor and the stored electrostatic potential energy is revealed to only partially contribute to the electrowetting.

Communication: Modeling electrolyte mixtures with concentration dependent dielectric permittivity

NASA Astrophysics Data System (ADS)

Chen, Hsieh; Panagiotopoulos, Athanassios Z.

2018-01-01

We report a new implicit-solvent simulation model for electrolyte mixtures based on the concept of concentration dependent dielectric permittivity. A combining rule is found to predict the dielectric permittivity of electrolyte mixtures based on the experimentally measured dielectric permittivity for pure electrolytes as well as the mole fractions of the electrolytes in mixtures. Using grand canonical Monte Carlo simulations, we demonstrate that this approach allows us to accurately reproduce the mean ionic activity coefficients of NaCl in NaCl-CaCl2 mixtures at ionic strengths up to I = 3M. These results are important for thermodynamic studies of geologically relevant brines and physiological fluids.

Electrode effects in dielectric spectroscopy of colloidal suspensions

NASA Astrophysics Data System (ADS)

Cirkel, P. A.; van der Ploeg, J. P. M.; Koper, G. J. M.

1997-02-01

We present a simple model to account for electrode polarization in colloidal suspensions. Apart from correctly predicting the ω {-3}/{2} dependence for the dielectric permittivity at low frequencies ω, the model provides an explicit dependence of the effect on electrode spacing. The predictions are tested for the sodium bis(2-ethylhexyl) sulfosuccinate (AOT) water-in-oil microemulsion with iso-octane as continuous phase. In particular, the dependence of electrode polarization effects on electrode spacing has been measured and is found to be in accordance with the model prediction. Methods to reduce or account for electrode polarization are briefly discussed.

Comparison of Rising Resonator Relative Permittivity Measurements to Ground Penetrating Radar Data

DTIC Science & Technology

2014-04-01

permittivity of the soil and the target is critical in determining the strength of the reflection from the target. In this paper, a microstrip ring resonator...is used to measure the relative permittivity of the soil and various target fill materials. For this measurement technique, a microstrip ring... antennas of varying frequencies to take measurements of the two port transmission coefficient. This coefficient is measured from the input feedline to

Comparison of Ring Resonator Relative Permittivity Measurements to Ground Penetrating Radar Data

DTIC Science & Technology

2014-04-01

permittivity of the soil and the target is critical in determining the strength of the reflection from the target. In this paper, a microstrip ring resonator...is used to measure the relative permittivity of the soil and various target fill materials. For this measurement technique, a microstrip ring... antennas of varying frequencies to take measurements of the two port transmission coefficient. This coefficient is measured from the input feedline to

Electromagnetic van Kampen waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ignatov, A. M., E-mail: aign@fpl.gpi.ru

2017-01-15

The theory of van Kampen waves in plasma with an arbitrary anisotropic distribution function is developed. The obtained solutions are explicitly expressed in terms of the permittivity tensor. There are three types of perturbations, one of which is characterized by the frequency dependence on the wave vector, while for the other two, the dispersion relation is lacking. Solutions to the conjugate equations allowing one to solve the initial value problem are analyzed.

Analytical solution for the effect of the permittivity of coating layer on eddy current generated in an aluminum sample by EMAT

NASA Astrophysics Data System (ADS)

Sun, Feiran; Sun, Zhenguo; Chen, Qiang

2016-02-01

In order to improve the ultrasonic wave amplitude excited by electromagnetic acoustic transducers (EMATs), many researchers have proposed models. But they always ignored displacement current or the effect of the permittivity of the air or the metal sample during modeling, due to its low permittivity. However, more durable dielectric materials are replacing or coating with metals in many applications which have a much higher permittivity than air or metal sample so that the effect of permittivity cannot be ignored. Based on an analytical model, the effect of the permittivity of coating layer on the eddy current generated in an aluminum sample by EMAT has been studied. The analytical analysis indicates that the eddy current density excited by the spiral coil of EMAT slowly increases in the beginning and then decreases rapidly while the permittivity increases, and it has much relation to the thickness of the coating layer and the exciting frequency, which is verified by the simulation result.

Dielectric Relaxation In Complex Perovskite Sm(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Nishant; Prasad, S.; Sinha, T. P.

2011-11-22

The complex perovskite oxide Samarium nickel titenate, Sm(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}(SNT) is synthesized by a solid-state reaction technique. The X-ray diffraction of the sample at room temperature shows a monoclinic phase. The scanning micrograph of the sample shows the average grain size{approx_equal}0.6{mu}m The field dependence of dielectric response and the loss tangent of the sample are measured in a frequency range from 100Hz to 1MHz and in a temperature range from 313 K to 673 K. An analysis of the real and imaginary parts of the dielectric permittivity with frequency is performed, assuming a distribution of relaxation times as confirmedmore » by Cole-Cole plots. The frequency dependent electrical data are analyzed in the framework of conductivity formalism. The frequency dependent conductivity data are fitted to the universal power law. All these formalisms provided for qualitative similarities in the relaxation times.« less

Microwave Dielectric Properties of Alfalfa Leaves From 0.3 to 18 GHz

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 upmore » 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.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ci, Penghong; Liu, Guoxi; Dong, Shuxiang, E-mail: sxdong@pku.edu.cn

We report a strain-mediated electric field manipulation of permittivity in BaTiO{sub 3} (barium titanate, BT) ceramic by a Pb(Zr,Ti)O{sub 3} (PZT) bimorph. This BT/PZT heterostructure exhibited a relatively large permittivity tunability of BT up to ±10% in a wide frequency range under an electric field of ±4 kV/cm applied to the PZT bimorph. The permittivity tunability is attributed to the strain in BT produced by the PZT bimorph. Calculations of the relationship between permittivity and applied electric field were developed, and corresponded well with measurements. The BT/PZT heterostructure has potential for applications in broadband field tunable smart electronic devices.

Influence of the electron intrinsic magnetic moment on the transverse dielectric permittivity of degenerate electron gas

NASA Astrophysics Data System (ADS)

Maslov, S. A.; Bobrov, V. B.; Kirillin, A. V.; Trigger, S. A.

2018-01-01

Using the linear response theory, the transverse dielectric permittivity of a homogeneous and isotropic system of charged particles is considered. In the ideal gas approximation for the polarization function, an explicit analytical expression for the transverse permittivity of a degenerate electron plasma, which takes into account electron spin, is found. This result describes both the Landau diamagnetism and Pauli paramagnetism in electron plasma. The influence of the electron intrinsic magnetic moment on the spatial and frequency dispersion of the transverse dielectric permittivity of degenerate electron plasma is numerically studied, that is crucial for determining the optical characteristics of plasma.

Millimeter-wave sensor based on a λ/2-line resonator for identification and dielectric characterization of non-ionic surfactants

PubMed Central

Rodilla, H.; Kim, A. A.; Jeffries, G. D. M.; Vukusic, J.; Jesorka, A.; Stake, J.

2016-01-01

Studies of biological and artificial membrane systems, such as niosomes, currently rely on the use of fluorescent tags, which can influence the system under investigation. For this reason, the development of label-free, non-invasive detection techniques is of great interest. We demonstrate an open-volume label-free millimeter-wave sensing platform based on a coplanar waveguide, developed for identification and characterization of niosome constituents. A design based on a λ/2-line resonator was used and on-wafer measurements of transmission and reflection parameters were performed up to 110 GHz. Our sensor was able to clearly distinguish between common niosome constituents, non-ionic surfactants Tween 20 and Span 80, measuring a resonance shift of 3 GHz between them. The complex permittivities of the molecular compounds have been extracted. Our results indicate insignificant frequency dependence in the investigated frequency range (3 GHz – 110 GHz). Values of permittivity around 3.0 + 0.7i and 2.2 + 0.4i were obtained for Tween 20 and Span 80, respectively. PMID:26786983

Millimeter-wave sensor based on a λ/2-line resonator for identification and dielectric characterization of non-ionic surfactants.

PubMed

Rodilla, H; Kim, A A; Jeffries, G D M; Vukusic, J; Jesorka, A; Stake, J

2016-01-20

Studies of biological and artificial membrane systems, such as niosomes, currently rely on the use of fluorescent tags, which can influence the system under investigation. For this reason, the development of label-free, non-invasive detection techniques is of great interest. We demonstrate an open-volume label-free millimeter-wave sensing platform based on a coplanar waveguide, developed for identification and characterization of niosome constituents. A design based on a λ/2-line resonator was used and on-wafer measurements of transmission and reflection parameters were performed up to 110 GHz. Our sensor was able to clearly distinguish between common niosome constituents, non-ionic surfactants Tween 20 and Span 80, measuring a resonance shift of 3 GHz between them. The complex permittivities of the molecular compounds have been extracted. Our results indicate insignificant frequency dependence in the investigated frequency range (3 GHz - 110 GHz). Values of permittivity around 3.0 + 0.7i and 2.2 + 0.4i were obtained for Tween 20 and Span 80, respectively.

Impedance-spectroscopy analysis of a LiTaO{sub 3}-type single crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ming, D.; Reau, J.M.; Ravez, J.

1995-04-01

Low-frequency dielectric dispersion phenomena in a LiTaO{sub 3}-type single crystal have been analyzed by impedance spectroscopy in directions parallel and perpendicular to the polar c-axis (rhombohedral system). An empirical expression has been deduced for the complex permittivity {epsilon}*({omega}), {epsilon}*({omega}) = {epsilon}{infinity} + {sup {epsilon}{sub s}-{epsilon}{infinity}}/{sub 1 + (i{omega}/{omega}{sub 1}){sup m}} + {sup {sigma}{sub 0}}/{sub {epsilon}{sub 0}{omega}} [1 + (i{omega}/{omega}{sub 2}){sup n}], where the ({omega}{sub 1}, m) and ({omega}{sub 2}, n) couples characterize respectively the lattice and the charge carrier responses. This relation may be considered as a generalization of the Cole-Cole dielectric expression. Excellent agreement has been obtained in amore » wide frequency domain (1-10{sup 6} Hz) between the measured and calculated permittivities in the 500-650{degrees}C temperature range ({Tc} = 600{degrees}C). The temperature dependence of various dielectrical parameters has been determined and discussed. The relaxations are correlated to Li atom motions.« less

Radio frequency (RF) microwave components and subsystems using loaded ridge waveguide

DOEpatents

Kang, Yoon W.

2013-08-20

A waveguide having a non-conductive material with a high permeability (.mu., .mu..sub.r for relative permeability) and/or a high permittivity (.di-elect cons., .di-elect cons..sub.r for relative permittivity) positioned within a housing. When compared to a hollow waveguide, the waveguide of this invention, reduces waveguide dimensions by .varies..mu. ##EQU00001## The waveguide of this invention further includes ridges which further reduce the size and increases the usable frequency bandwidth.

Relating ground truth collection to model sensitivity

NASA Technical Reports Server (NTRS)

Amar, Faouzi; Fung, Adrian K.; Karam, Mostafa A.; Mougin, Eric

1993-01-01

The importance of collecting high quality ground truth before a SAR mission over a forested area is two fold. First, the ground truth is used in the analysis and interpretation of the measured backscattering properties; second, it helps to justify the use of a scattering model to fit the measurements. Unfortunately, ground truth is often collected based on visual assessment of what is perceived to be important without regard to the mission itself. Sites are selected based on brief surveys of large areas, and the ground truth is collected by a process of selecting and grouping different scatterers. After the fact, it may turn out that some of the relevant parameters are missing. A three-layer canopy model based on the radiative transfer equations is used to determine, before hand, the relevant parameters to be collected. Detailed analysis of the contribution to scattering and attenuation of various forest components is carried out. The goal is to identify the forest parameters which most influence the backscattering as a function of frequency (P-, L-, and C-bands) and incident angle. The influence on backscattering and attenuation of branch diameters, lengths, angular distribution, and permittivity; trunk diameters, lengths, and permittivity; and needle sizes, their angular distribution, and permittivity are studied in order to maximize the efficiency of the ground truth collection efforts. Preliminary results indicate that while a scatterer may not contribute to the total backscattering, its contribution to attenuation may be significant depending on the frequency.

Effect of zinc oxide nanoparticles on dielectric behavior of nematic liquid crystal

NASA Astrophysics Data System (ADS)

Sharma, Amit; Kumar, Pankaj; Malik, Praveen

2018-05-01

In this work, phase transition and dielectric behavior of nematic liquid crystal (NLC), E7 and zinc oxide (ZnO) nanoparticles (NPs) doped nematic liquid crystals are investigated. Effect of nano-particles dispersion is analyzed and compared with the dielectric behavior of E7 and E7-ZnO. Frequency dependent dielectric permittivity at various temperatures in nematic phase for E7 and E7-ZnO sample is also studied.

A planar transmission-line sensor for measuring the microwave permittivity of liquid and semisolid biological materials

USDA-ARS?s Scientific Manuscript database

A planar transmission-line configuration for rapid, nondestructive, wideband permittivity measurements of liquid and semisolid materials at microwave frequencies is described. The transmission-line propagation constant of the proposed configuration is determined with the multiline technique from sca...

Contribution of nanointerfaces to colossal permittivity of doped Ba(Ti,Sn)O3 ceramics

NASA Astrophysics Data System (ADS)

V'yunov, Oleg; Reshytko, Borys; Belous, Anatolii; Kovalenko, Leonid

2018-03-01

The microstructure, crystal chemical parameters and electrical-physical properties of samples of barium titanate-based dielectric and semiconductor ceramics were investigated in a wide frequency range. The contributions of different nanointerfaces to the permittivity of samples under investigation have been determined.

An electrohydrodynamic flow in ac electrowetting.

PubMed

Lee, Horim; Yun, Sungchan; Ko, Sung Hee; Kang, Kwan Hyoung

2009-12-17

In ac electrowetting, hydrodynamic flows occur within a droplet. Two distinct flow patterns were observed, depending on the frequency of the applied electrical signal. The flow at low-frequency range was explained in terms of shape oscillation and a steady streaming process in conjunction with contact line oscillation. The origin of the flow at high-frequency range has not yet been explained. We suggest that the high-frequency flow originated mainly from the electrothermal effect, in which electrical charge is generated due to the gradient of electrical conductivity and permittivity, which is induced by the Joule heating of fluid medium. To support our argument, we analyzed the flow field numerically while considering the electrical body force generated by the electrothermal effect. We visualized the flow pattern and measured the flow velocity inside the droplet. The numerical results show qualitative agreement with experimental results with respect to electric field and frequency dependence of flow velocity. The effects of induced-charge electro-osmosis, natural convection, and the Marangoni flow are discussed.

Optical performance and metallic absorption in nanoplasmonic systems.

PubMed

Arnold, Matthew D; Blaber, Martin G

2009-03-02

Optical metrics relating to metallic absorption in representative plasmonic systems are surveyed, with a view to developing heuristics for optimizing performance over a range of applications. We use the real part of the permittivity as the independent variable; consider strengths of particle resonances, resolving power of planar lenses, and guiding lengths of planar waveguides; and compare nearly-free-electron metals including Al, Cu, Ag, Au, Li, Na, and K. Whilst the imaginary part of metal permittivity has a strong damping effect, field distribution is equally important and thus factors including geometry, real permittivity and frequency must be considered when selecting a metal. Al performs well at low permittivities (e.g. sphere resonances, superlenses) whereas Au & Ag only perform well at very negative permittivities (shell and rod resonances, LRSPP). The alkali metals perform well overall but present engineering challenges.

High precision slotted cavity measurement of a novel ceramic state polymer electrolyte

NASA Astrophysics Data System (ADS)

Quan, Wei; NurulAfsar, Mohammed

2018-01-01

Thin film materials are already used in a variety of microwave and higher frequency applications such as electrically tunable microwave devices, integrated circuits like MMICs, radomes, and radar absorbing coating. The determination of the dielectric properties of these films is thus of significant importance. The measurement of complex dielectric permittivity of thin films is very difficult at microwave, millimeter, and THz frequencies because both the amplitude change and phase shift are not large enough to evaluate the real part of the dielectric permittivity. A specially designed transverse slotted cavity for X-band microwave measurement has been designed and constructed to employ with a vector network analyzer to evaluate the real part of dielectric permittivity of thin films accurately and conveniently. Commercially available polymer thin films are measured to validate the methods.

[Support vector machine?assisted diagnosis of human malignant gastric tissues based on dielectric properties].

PubMed

Zhang, Sa; Li, Zhou; Xin, Xue-Gang

2017-12-20

To achieve differential diagnosis of normal and malignant gastric tissues based on discrepancies in their dielectric properties using support vector machine. The dielectric properties of normal and malignant gastric tissues at the frequency ranging from 42.58 to 500 MHz were measured by coaxial probe method, and the Cole?Cole model was used to fit the measured data. Receiver?operating characteristic (ROC) curve analysis was used to evaluate the discrimination capability with respect to permittivity, conductivity, and Cole?Cole fitting parameters. Support vector machine was used for discriminating normal and malignant gastric tissues, and the discrimination accuracy was calculated using k?fold cross? The area under the ROC curve was above 0.8 for permittivity at the 5 frequencies at the lower end of the measured frequency range. The combination of the support vector machine with the permittivity at all these 5 frequencies combined achieved the highest discrimination accuracy of 84.38% with a MATLAB runtime of 3.40 s. The support vector machine?assisted diagnosis is feasible for human malignant gastric tissues based on the dielectric properties.

Low-loss Z-type barium hexaferrite composites from nanoscale ZnAl2O4 addition for high-frequency applications

NASA Astrophysics Data System (ADS)

Zheng, Zongliang; Feng, Quanyuan; Harris, Vincent G.

2018-05-01

In this study, nanocrystalline ZnAl2O4 (ZA) were introduced to Z-type barium hexaferrite (Co2Z) and the effects of ZA addition upon the crystal-phase composition, microstructure, permeability and permittivity as well as losses characteristics over a wide frequency range of 10 MHz-1 GHz have been systematically investigated. With increasing ZA content (x) from 0 to 15 wt%, the permeability μ' at low frequencies decreased from 12.0 to 4.3, while the permittivity ɛ' was decreased from 27.4 to 10.7. Correspondingly, the frequency stability of permeability and permittivity were improved and the losses were effectively reduced. When x is in the range of 5-10 wt%, the magnetic loss tan δμ is in the order of 10-2 and the dielectric loss tan δɛ is in the order of 10-3 at 300 MHz, which is lower by one order of magnitude compared with that of undoped Co2Z. The modified magnetic and dielectric properties are closely related to the changing phase composition and microstructure.

Dielectric discontinuity at interfaces in the atomic-scale limit: permittivity of ultrathin oxide films on silicon.

PubMed

Giustino, Feliciano; Umari, Paolo; Pasquarello, Alfredo

2003-12-31

Using a density-functional approach, we study the dielectric permittivity across interfaces at the atomic scale. Focusing on the static and high-frequency permittivities of SiO2 films on silicon, for oxide thicknesses from 12 A down to the atomic scale, we find a departure from bulk values in accord with experiment. A classical three-layer model accounts for the calculated permittivities and is supported by the microscopic polarization profile across the interface. The local screening varies on length scales corresponding to first-neighbor distances, indicating that the dielectric transition is governed by the chemical grading. Silicon-induced gap states are shown to play a minor role.

Permeability measurement and control for epoxy composites

NASA Astrophysics Data System (ADS)

Chang, Tsun-Hsu; Tsai, Cheng-Hung; Wong, Wei-Syuan; Chen, Yen-Ren; Chao, Hsien-Wen

2017-08-01

The coupling of the electric and magnetic fields leads to a strong interplay in materials' permittivity and permeability. Here, we proposed a specially designed cavity, called the mu cavity. The mu cavity, consisting of a mushroom structure inside a cylindrical resonator, is exclusively sensitive to permeability, but not to permittivity. It decouples materials' electromagnetic properties and allows an accurate measurement of the permeability. With the help of an epsilon cavity, these two cavities jointly determine the complex permeability and permittivity of the materials at microwave frequencies. Homemade epoxy-based composite materials were prepared and tested. Measurement and manipulation of the permeability and permittivity of the epoxy composites will be shown. The results will be compared with the effective medium theories.

Polyimide/nanosized CaCu3Ti4O12 functional hybrid films with high dielectric permittivity

NASA Astrophysics Data System (ADS)

Yang, Yang; Zhu, Ben-Peng; Lu, Zhi-Hong; Wang, Zi-Yu; Fei, Chun-Long; Yin, Di; Xiong, Rui; Shi, Jing; Chi, Qing-Guo; Lei, Qing-Quan

2013-01-01

This work reports the high dielectric permittivity of polyimide (PI) embedded with CaCu3Ti4O12 (CCTO) nanoparticles. The dielectric behavior has been investigated over a frequency of 100 Hz-1 MHz. High dielectric permittivity (ɛ = 171) and low dielectric loss (tan δ = 0.45) at 100 Hz have been observed near the percolation threshold. The experimental results fit well with the Percolation theory. We suggest that the high dielectric permittivity originates from the large interface area and the remarkable Maxwell-Wagner-Sillars effect at percolation in which nomadic charge carriers are blocked at internal interfaces between CCTO nanoparticles and the polyimide matrix.

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

DOE PAGES

Trepakov, V. A.; Kvyatkovskii, O. E.; Savinov, M. E.; ...

2016-10-01

The unusual behavior of the low-frequency (10 Hz–1 MHz) permittivity in single crystals of ferroelectric multiferroic TbMnO3 has been experimentally and theoretically studied in detail in the region of the narrow temperature peak of the permittivity, associated with the ferroelectric phase transition (T C ~ 27.4 K). It has been found that the ε c(ω, T) maximum sharply decreases with increasing measured field frequency, while the temperature position of the maximum is independent of frequency. It has been shown that the observed features of the polarization response can be satisfactorily described within the Landau–Khalatnikov polarization relaxation theory.

Terahertz frequency superconductor-nanocomposite photonic band gap

NASA Astrophysics Data System (ADS)

Elsayed, Hussein A.; Aly, Arafa H.

2018-02-01

In the present work, we discuss the transmittance properties of one-dimensional (1D) superconductor nanocomposite photonic crystals (PCs) in THz frequency regions. Our modeling is essentially based on the two-fluid model, Maxwell-Garnett model and the characteristic matrix method. The numerical results investigate the appearance of the so-called cutoff frequency. We have obtained the significant effect of some parameters such as the volume fraction, the permittivity of the host material, the size of the nanoparticles and the permittivity of the superconductor material on the properties of the cutoff frequency. The present results may be useful in the optical communications and photonic applications to act as tunable antenna in THz, reflectors and high-pass filter.

The Effect of Variation in Permittivity of Different Tissues on Induced Electric Field in the Brain during Transcranial Magnetic Stimulation

NASA Astrophysics Data System (ADS)

Hadimani, Ravi; Porzig, Konstantin; Crowther, Lawrence; Brauer, Hartmut; Toepfer, Hannes; Jiles, David; Department of Electrical and Computer Engineering, Iowa State University Team; Department of Advanced Electromagnetics, Ilmenau University of Technology Team

2013-03-01

Estimation of electric field in the brain during Transcranial Magnetic Stimulation (TMS) requires knowledge of the electric property of brain tissue. Grey and white matters have unusually high relative permittivities of ~ 106 at low frequencies. However, relative permittivity of cerebrospinal fluid is ~ 102. With such a variation it is necessary to consider the effect of boundaries. A model consisting of 2 hemispheres was used in the model with the properties of one hemisphere kept constant at σ1 = 0.1Sm-1 and ɛr 1 = 10 while the properties of the second hemisphere were changed kept at σ2 = 0.1Sm-1 to 2Sm-1 and ɛr 2 = 102 to 105. A 70 mm diameter double coil was used as the source of the magnetic field. The amplitude of the current in the coil was 5488 A at a frequency of 2.9 kHz. The results show that the electric field, E induced during magnetic stimulation is independent of the relative permittivity, ɛr and varies with the conductivity. Thus the variation in E, calculated with homogeneous and heterogeneous head models was due to variation in conductivity of the tissues and not due to variation in permittivities.

Inverts permittivity and conductivity with structural constraint in GPR FWI based on truncated Newton method

NASA Astrophysics Data System (ADS)

Ren, Qianci

2018-04-01

Full waveform inversion (FWI) of ground penetrating radar (GPR) is a promising technique to quantitatively evaluate the permittivity and conductivity of near subsurface. However, these two parameters are simultaneously inverted in the GPR FWI, increasing the difficulty to obtain accurate inversion results for both parameters. In this study, I present a structural constrained GPR FWI procedure to jointly invert the two parameters, aiming to force a structural relationship between permittivity and conductivity in the process of model reconstruction. The structural constraint is enforced by a cross-gradient function. In this procedure, the permittivity and conductivity models are inverted alternately at each iteration and updated with hierarchical frequency components in the frequency domain. The joint inverse problem is solved by the truncated Newton method which considering the effect of Hessian operator and using the approximated solution of Newton equation to be the perturbation model in the updating process. The joint inversion procedure is tested by three synthetic examples. The results show that jointly inverting permittivity and conductivity in GPR FWI effectively increases the structural similarities between the two parameters, corrects the structures of parameter models, and significantly improves the accuracy of conductivity model, resulting in a better inversion result than the individual inversion.

Relaxation phenomena in AOT-water-decane critical and dense microemulsions

NASA Astrophysics Data System (ADS)

Letamendia, L.; Pru-Lestret, E.; Panizza, P.; Rouch, J.; Sciortino, F.; Tartaglia, P.; Hashimoto, C.; Ushiki, H.; Risso, D.

2001-11-01

We report on extensive measurements of the low and high frequencies sound velocity and sound absorption in AOT-water-decane microemulsions deduced from ultrasonic and, for the first time as far as the absorption is concerned, from Brillouin scattering experiments. New experimental results on dielectric relaxation are also reported. Our results, which include data taken for critical as well as dense microemulsions, show new interesting relaxation phenomena. The relaxation frequencies deduced from very high frequency acoustical measurements are in good agreement with new high frequency dielectric relaxation measurements. We show that along the critical isochore, sound dispersion, relaxation frequency, and static dielectric permittivity can be accurately fitted to power laws. The absolute values of the new exponents we derived from experimental data are nearly equal, and they are very close to β=0.33 characterising the shape of the coexistence curve. The exponent characterising the infinite frequency permittivity is very close to 0.04 relevant to the diverging shear viscosity. For dense microemulsions, two well defined relaxation domains have been identified and the temperature variations of the sound absorption and the zero frequency dielectric permittivity bear striking similarities. We also show that the relaxation frequency of the slow relaxation process is almost independent of temperature and volume fraction and so cannot be attributed to percolation phenomena, whereas it can more likely be attributed to an intrinsic relaxation process probably connected to membrane fluctuations.

Dielectric properties of lunar surface

NASA Astrophysics Data System (ADS)

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

2017-03-01

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

Inferences on hydrogen bond networks in water from isopermitive frequency investigations.

PubMed

Geethu, P M; Ranganathan, Venketesh T; Satapathy, Dillip K Kumar

2018-06-26

Intermolecular hydrogen bonds play a crucial role in determining the unique characteristics of liquid water. We present low-frequency (1 Hz - 40 MHz) dielectric spectroscopic investigations on water in the presence and absence of added solutes at different temperatures from 10°C to 60°C. The intersection points of temperature dependent permittivity contours at the vicinity of isopermitive frequency (IPF) in water are recorded and its properties are presumed to be related to the extent of hydrogen bond networks in water. IPF is defined as the frequency at which the relative permittivity of water is almost independent of temperature. The set of intersection points of temperature dependent permittivity contours at the vicinity of IPF are characterized by the mean (M_IPF) and root-mean-square deviation/standard deviation (σ_IPF ) associated with IPF. The tunability of M_IPF by the addition of NaCl salt emphasizes the strong correlation between the concentration of ions in water and the M_IPF . The σ_IPF is surmised to be related to the orientational correlations of water dipoles as well as to the intermolecular hydrogen bond networks in water. Further, alterations in σ_IPF is observed with the addition of kosmotropic and chaotropic solutes into water and are thought to arise due to the restructuring of hydrogen bond networks in water in presence of added solutes. Notably, the solute induced reconfiguration of hydrogen bond networks in water or often-discussed structure making/breaking effects of the added solutes in water can be inferred, albeit qualitatively, by examining the M_IPF and σ_IPF. Further, the Gaussian deconvoluted OH-stretching modes present in the Raman Spectra of water and aqueous solutions of IPA and DMF strongly endorses the structural rearrangements occurring in water in presence of kosmotropes and chaotropes and are in-line with the results derived from the root-mean-square deviation in IPF. . © 2018 IOP Publishing Ltd.

Molding of Plasmonic Resonances in Metallic Nanostructures: Dependence of the Non-Linear Electric Permittivity on System Size and Temperature

PubMed Central

Alabastri, Alessandro; Tuccio, Salvatore; Giugni, Andrea; Toma, Andrea; Liberale, Carlo; Das, Gobind; De Angelis, Francesco; Di Fabrizio, Enzo; Zaccaria, Remo Proietti

2013-01-01

In this paper, we review the principal theoretical models through which the dielectric function of metals can be described. Starting from the Drude assumptions for intraband transitions, we show how this model can be improved by including interband absorption and temperature effect in the damping coefficients. Electronic scattering processes are described and included in the dielectric function, showing their role in determining plasmon lifetime at resonance. Relationships among permittivity, electric conductivity and refractive index are examined. Finally, a temperature dependent permittivity model is presented and is employed to predict temperature and non-linear field intensity dependence on commonly used plasmonic geometries, such as nanospheres. PMID:28788366

Origin of colossal permittivity in BaTiO3 via broadband dielectric spectroscopy

NASA Astrophysics Data System (ADS)

Han, Hyuksu; Voisin, Christophe; Guillemet-Fritsch, Sophie; Dufour, Pascal; Tenailleau, Christophe; Turner, Christopher; Nino, Juan C.

2013-01-01

Barium titanate (BT) ceramics with Ba/Ti ratios of 0.95 and 1.00 were synthesized using spark plasma sintering (SPS) technique. Dielectric spectroscopy (frequency range from 40 Hz to 1 MHz and temperature range from 300 K to 30 K) was performed on those ceramics (SPS BT). SPS BT showed extremely high permittivity up to ˜105, which can be referred to as colossal permittivity, with relatively low dielectric loss of ˜0.05. Data analyses following Debye relaxation and universal dielectric response models indicate that the origin of colossal permittivity in BT ceramics is the result of a hopping polaron within semiconducting grains in combination with interfacial polarization at the insulating grain boundary. Furthermore, the contributions of each polarization mechanism to the colossal permittivity in SPS BT, such as a hopping polarization, internal barrier layer capacitance effect, and electrode effect, were estimated.

A multi-frequency radiometric measurement of soil moisture content over bare and vegetated fields

NASA Technical Reports Server (NTRS)

Wang, J. R.; Schmugge, T. J.; Gould, W. I.; Glazar, W. S.; Fuchs, J. E.; Mcmurtrey, J. E., III

1982-01-01

An experiment on soil moisture remote sensing was conducted during July to September 1981 on bare, grass, and alfalfa fields at frequencies of 0.6, 1.4, 5.0, and 10.6 GHz with radiometers mounted on mobile towers. The results confirm the frequency dependence of sensitivity reduction due to the presence of vegetation cover. For the type of vegetated fields reported here, the vegetation effect is appreciable even at 0.6 GHz. Measurements over bare soil show that when the soil is wet, the measured brightness temperature is lowest at 5.0 GHz and highest at 0.6 GHz, a result contrary to the expectation based on the estimated dielectric permittivity of soil-water mixtures and the current radiative transfer model in that frequency range.

Dielectric properties and activation behavior of gadolinium doped nanocrystalline yttrium chromite

NASA Astrophysics Data System (ADS)

Sinha, R.; Basu, S.; Meikap, A. K.

2018-04-01

Gadolinium doped Yttrium Chromite nanoparticles are synthesized following sol-gel method. The formation of the nanoparticles are confirmed by XRD and TEM measurements. Dielectric permittivity and dielectric loss are estimated within the temperature range 298K to 523K and in the frequency range 20 Hz to 1 MHz. Dielectric permittivity follows the power law ɛ'(f) ∝ Tm. It is observed that the temperature exponent m increases with the decreasing frequency. The temperature variation of resistivity shows that the samples have semiconducting behavior. The activation energy is also measured.

Optically transparent frequency selective surfaces on flexible thin plastic substrates

NASA Astrophysics Data System (ADS)

Dewani, Aliya A.; O'Keefe, Steven G.; Thiel, David V.; Galehdar, Amir

2015-02-01

A novel 2D simple low cost frequency selective surface was screen printed on thin (0.21 mm), flexible transparent plastic substrate (relative permittivity 3.2). It was designed, fabricated and tested in the frequency range 10-20 GHz. The plane wave transmission and reflection coefficients agreed with numerical modelling. The effective permittivity and thickness of the backing sheet has a significant effect on the frequency characteristics. The stop band frequency reduced from 15GHz (no backing) to 12.5GHz with polycarbonate. The plastic substrate thickness beyond 1.8mm has minimal effect on the resonant frequency. While the inner element spacing controls the stop-band frequency, the substrate thickness controls the bandwidth. The screen printing technique provided a simple, low cost FSS fabrication method to produce flexible, conformal, optically transparent and bio-degradable FSS structures which can find their use in electromagnetic shielding and filtering applications in radomes, reflector antennas, beam splitters and polarizers.

Estimating porosity and solid dielectric permittivity in the Miami Limestone using high-frequency ground penetrating radar (GPR) measurements at the laboratory scale

NASA Astrophysics Data System (ADS)

Mount, Gregory J.; Comas, Xavier

2014-10-01

Subsurface water flow in South Florida is largely controlled by the heterogeneous nature of the karst limestone in the Biscayne aquifer and its upper formation, the Miami Limestone. These heterogeneities are amplified by dissolution structures that induce changes in the aquifer's material and physical properties (i.e., porosity and dielectric permittivity) and create preferential flow paths. Understanding such patterns are critical for the development of realistic groundwater flow models, particularly in the Everglades, where restoration of hydrological conditions is intended. In this work, we used noninvasive ground penetrating radar (GPR) to estimate the spatial variability in porosity and the dielectric permittivity of the solid phase of the limestone at centimeter-scale resolution to evaluate the potential for field-based GPR studies. A laboratory setup that included high-frequency GPR measurements under completely unsaturated and saturated conditions was used to estimate changes in electromagnetic wave velocity through Miami Limestone samples. The Complex Refractive Index Model was used to derive estimates of porosity and dielectric permittivity of the solid phase of the limestone. Porosity estimates of the samples ranged between 45.2 and 66.0% and showed good correspondence with estimates of porosity using analytical and digital image techniques. Solid dielectric permittivity values ranged between 7.0 and 13.0. This study shows the ability of GPR to image the spatial variability of porosity and dielectric permittivity in the Miami Limestone and shows potential for expanding these results to larger scales and other karst aquifers.

Origin of giant dielectric permittivity and weak ferromagnetic behavior in (1-x)LaFeO3-xBaTiO3 (0.0 ≤ x ≤ 0.25) solid solutions

NASA Astrophysics Data System (ADS)

Sreenivasu, T.; Tirupathi, P.; Prabahar, K.; Suryanarayana, B.; Chandra Mouli, K.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veklenko, B. A., E-mail: veklenkoba@yandex.ru

It is shown theoretically that the electromagnetic background of longitudinal zero oscillations of a temperature-degenerate electron–ion plasma in a thermodynamic equilibrium state resonantly distorts the wave functions of its electrons. This gives rise to a characteristic quantum frequency that nonanalytically depends on Planck’s constant ℏ. Vacuum phenomena in plasma attributed to zero oscillations turn out to be anomalously large. Quantum corrections to the transverse dielectric permittivity of a degenerate electron–ion plasma, which are nonanalytic with respect to ℏ and are attributed to the zero-point oscillations of the plasma, are determined.

Absorption Properties of Supercooled Liquid Water between 31 and 225 GHz: Evaluation of Absorption Models Using Ground-Based Observations

DOE PAGES

Kneifel, Stefan; Redl, Stephanie; Orlandi, Emiliano; ...

2014-04-10

Microwave radiometers (MWR) are commonly used to quantify the amount of supercooled liquid water (SLW) in clouds; however, the accuracy of the SLW retrievals is limited by the poor knowledge of the SLW dielectric properties at microwave frequencies. Six liquid water permittivity models were compared with ground-based MWR observations between 31 and 225 GHz from sites in Greenland, the German Alps, and a low-mountain site; average cloud temperatures of observed thin cloud layers range from 0° to –33°C. A recently published method to derive ratios of liquid water opacity from different frequencies was employed in this analysis. These ratios aremore » independent of liquid water path and equal to the ratio of αL at those frequencies that can be directly compared with the permittivity model predictions. The observed opacity ratios from all sites show highly consistent results that are generally within the range of model predictions; however, none of the models are able to approximate the observations over the entire frequency and temperature range. Findings in earlier published studies were used to select one specific model as a reference model for αL at 90 GHz; together with the observed opacity ratios, the temperature dependence of αL at 31.4, 52.28, 150, and 225 GHz was derived. The results reveal that two models fit the opacity ratio data better than the other four models, with one of the two models fitting the data better for frequencies below 90 GHz and the other for higher frequencies. Furthermore, these findings are relevant for SLW retrievals and radiative transfer in the 31–225-GHz frequency region.« less

Microstrip Patch Sensor for Salinity Determination.

PubMed

Lee, Kibae; Hassan, Arshad; Lee, Chong Hyun; Bae, Jinho

2017-12-18

In this paper, a compact microstrip feed inset patch sensor is proposed for measuring the salinities in seawater. The working principle of the proposed sensor depends on the fact that different salinities in liquid have different relative permittivities and cause different resonance frequencies. The proposed sensor can obtain better sensitivity to salinity changes than common sensors using conductivity change, since the relative permittivity change to salinity is 2.5 times more sensitive than the conductivity change. The patch and ground plane of the proposed sensor are fabricated by conductive copper spray coating on the masks made by 3D printer. The fabricated patch and the ground plane are bonded to a commercial silicon substrate and then attached to 5 mm-high chamber made by 3D printer so that it contains only 1 mL seawater. For easy fabrication and testing, the maximum resonance frequency was selected under 3 GHz and to cover salinities in real seawater, it was assumed that the salinity changes from 20 to 35 ppt. The sensor was designed by the finite element method-based ANSYS high-frequency structure simulator (HFSS), and it can detect the salinity with 0.01 ppt resolution. The designed sensor has a resonance frequency separation of 37.9 kHz and reflection coefficients under -20 dB at the resonant frequencies. The fabricated sensor showed better performance with average frequency separation of 48 kHz and maximum reflection coefficient of -35 dB. By comparing with the existing sensors, the proposed compact and low-cost sensor showed a better detection capability. Therefore, the proposed patch sensor can be utilized in radio frequency (RF) tunable sensors for salinity determination.

Compressed perovskite aqueous mixtures near their phase transitions show very high permittivities: New prospects for high-field MRI dielectric shimming.

PubMed

Neves, Ana L; Leroi, Lisa; Raolison, Zo; Cochinaire, Nicolas; Letertre, Thibaut; Abdeddaïm, Redha; Enoch, Stefan; Wenger, Jerome; Berthelot, Johann; Adenot-Engelvin, Anne-Lise; Malléjac, Nicolas; Mauconduit, Franck; Vignaud, Alexandre; Sabouroux, Pierre

2018-03-01

Perovskites are greatly used nowadays in many technological applications because of their high permittivity, more specifically in the form of aqueous solutions, for MRI dielectric shimming. In this study, full dielectric characterizations of highly concentrated CaTiO 3 /BaTiO 3 water mixtures were carried out and new permittivity maxima was reached. Permittivity measurements were done on aqueous solutions from 0%v/v to dry powder. The permittivity dependence with pressure was investigated. Scanning electron microscopy images were performed on a few representative solutions. BaTiO 3 pressed pads of different thicknesses, permittivities, and distances to the head were compared in a 7T MRI scanner. Perovskite aqueous mixtures undergo a pressure-dependent phase transition in terms of permittivity, with increasing water content. A new relative permittivity maximum of 475 was achieved. Microscopic images revealed structural differences between phases. A B1+ improvement in the temporal lobe was obtained with thin, high permittivity BaTiO 3 head. This new preparation method allows improved pad geometry and placement, as a result of the high relative permittivity values achieved. This method has great significance for medical applications of MRI dielectric shimming, being easy to replicate and implement on a large scale. Magn Reson Med 79:1753-1765, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

Adjusting Permittivity by Blending Varying Ratios of SWNTs

NASA Technical Reports Server (NTRS)

Tour, James M.; Stephenson, Jason J.; Higginbotham, Amanda

2012-01-01

A new composite material of singlewalled carbon nanotubes (SWNTs) displays radio frequency (0 to 1 GHz) permittivity properties that can be adjusted based upon the nanotube composition. When varying ratios of raw to functionalized SWNTs are blended into the silicone elastomer matrix at a total loading of 0.5 percent by weight, a target real permittivity value can be obtained between 70 and 3. This has particular use for designing materials for microwave lenses, microstrips, filters, resonators, high-strength/low-weight electromagnetic interference (EMI) shielding, antennas, waveguides, and low-loss magneto-dielectric products for applications like radome construction.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dewani, Aliya A., E-mail: a.ashraf@griffith.edu.au; O’Keefe, Steven G.; Thiel, David V.

A novel 2D simple low cost frequency selective surface was screen printed on thin (0.21 mm), flexible transparent plastic substrate (relative permittivity 3.2). It was designed, fabricated and tested in the frequency range 10-20 GHz. The plane wave transmission and reflection coefficients agreed with numerical modelling. The effective permittivity and thickness of the backing sheet has a significant effect on the frequency characteristics. The stop band frequency reduced from 15GHz (no backing) to 12.5GHz with polycarbonate. The plastic substrate thickness beyond 1.8mm has minimal effect on the resonant frequency. While the inner element spacing controls the stop-band frequency, the substratemore » thickness controls the bandwidth. The screen printing technique provided a simple, low cost FSS fabrication method to produce flexible, conformal, optically transparent and bio-degradable FSS structures which can find their use in electromagnetic shielding and filtering applications in radomes, reflector antennas, beam splitters and polarizers.« less

Wavelength-dependent excess permittivity as indicator of kerosene in diesel oil.

PubMed

Kanyathare, Boniphace; Peiponen, Kai-Erik

2018-04-20

Adulteration of diesel oil by kerosene is a serious problem because of air pollution resulting from car exhaust gases. The objective of this study was to develop a relatively simple optical measurement and data analysis method to screen low-adulterated diesel oils. For this purpose, we introduce the utilization of refractive index measurement with a refractometer, scanning of visible-near-infrared transmittance, transmittance data inversion using the singly subtractive Kramers-Kronig relation, and exploitation of so-called wavelength-dependent relative excess permittivity. It is shown for three different diesel oil grades, adulterated with kerosene, that the excess permittivity is a powerful measure for screening fake diesel oils. The excess relative permittivity of such binary mixtures also reveals hidden spectral fingerprints that are neither visible in dispersion data alone nor in spectral transmittance measurements alone. We believe that the excess permittivity data are useful in the case of screening adulteration of diesel oil by kerosene and can further be explored for practical sensing solutions, e.g., in quality inspection of diesel oils in refineries.

Mimicking Celestial Mechanics in Metamaterials

DTIC Science & Technology

2009-09-01

permittivities and permeabilities and could be related to light dynamics in curved space through the invariance of Maxwell’s equations under coordinate...transformations brings the equivalence between curved spacetime and local optical response through spatially dependent permeability and permittivity tensors...with local permeability and permittivity tensors given as µij = εij = δij h1h2h3 hi √g00 where hi= √gii are the Lame coefficients of the transformation

Study on the Microwave Permittivity of Single-Walled Carbon Nanotube

ERIC Educational Resources Information Center

Liu, Xiaolai; Zhao, Donglin

2009-01-01

In this article, we studied the microwave permittivity of the complex of the single-walled carbon nanotube and paraffin in 2-18GHz. In the range, the dielectric loss of single-walled carbon nanotube is higher, and the real part and the imaginary part of the dielectric constant decrease with the increase of frequency, and the dielectric constant…

Frequency Domain Modelling of Electromagnetic Wave Propagation in Layered Media

NASA Astrophysics Data System (ADS)

Schmidt, Felix; Lünenschloss, Peter; Mai, Juliane; Wagner, Norman; Töpfer, Hannes; Bumberger, Jan

2016-04-01

The amount of water in porous media such as soils and rocks is a key parameter when water resources are under investigation. Especially the quantitative spatial distribution and temporal evolution of water contents in soil formations are needed. In high frequency electromagnetic applications soil water content is quantitatively derived from the propagation behavior of electromagnetic waves along waveguides embedded in soil formations. The spatial distribution of the dielectric material properties along the waveguide can be estimated by numerical solving of the inverse problem based on the full wave forward model in time or frequency domain. However, current approaches mostly neglect or approximate the frequency dependence of the electromagnetic material properties of transfer function of the waveguide. As a first prove of concept a full two port broadband frequency domain forward model for propagation of transverse electromagnetic (TEM) waves in coaxial waveguide has been implemented. It is based on the propagation matrix approach for layered transmission line sections. Depending on the complexity of the material different models for the frequency dependent complex permittivity were applied. For the validation of the model a broadband frequency domain measurement with network analyzer technique was used. The measurement is based on a 20 cm long 50 Ohm 20/46 coaxial transmission line cell considering inhomogeneous material distributions. This approach allows (i) an increase of the waveguide calibration accuracy in comparison to conventional TDR based technique and (ii) the consideration of the broadband permittivity spectrum of the porous material. In order to systematic analyze the model, theoretical results were compared with measurements as well as 3D broadband finite element modeling of homogeneous and layered media in the coaxial transmission line cell. Defined standards (Teflon, dry glass beads, de-ionized water) were placed inside the line as the dielectric layers in different configurations. With a Thru Reflect Line calibration (TRL) the influences of connectors and adapters at the coaxial line sample holder were removed. The combination of the full two port calibration procedure and broadband modeling approach turns out to achieve a good accordance of modeling and experimental results. The next step is the implementation of an inversion to calculate the material parameters of every layer out of the s-parameters of the layered sample.

Frequency Domain Modelling of Electromagnetic Wave Propagation in Layered Media

NASA Astrophysics Data System (ADS)

Schmidt, Felix; Wagner, Norman; Lünenschloß, Peter; Toepfer, Hannes; Dietrich, Peter; Kaliorias, Andreas; Bumberger, Jan

2015-04-01

The amount of water in porous media such as soils and rocks is a key parameter when water resources are under investigation. Especially the quantitative spatial distribution and temporal evolution of water contents in soil formations are needed. In high frequency electromagnetic applications soil water content is quantitatively derived from the propagation behavior of electromagnetic waves along waveguides embedded in soil formations. The spatial distribution of the dielectric material properties along the waveguide can be estimated by numerical solving of the inverse problem based on the full wave forward model in time or frequency domain. However, current approaches mostly neglect or approximate the frequency dependence of the electromagnetic material properties of transfer function of the waveguide. As a first prove of concept a full two port broadband frequency domain forward model for propagation of transverse electromagnetic (TEM) waves in coaxial waveguide has been implemented. It is based on the propagation matrix approach for layered transmission line sections Depending on the complexity of the material different models for the frequency dependent complex permittivity were applied. For the validation of the model a broadband frequency domain measurement with network analyzer technique was used. The measurement is based on a 20 cm long 50 Ohm 20/46 coaxial transmission line cell considering inhomogeneous material distributions. This approach allows (i) an increase of the waveguide calibration accuracy in comparison to conventional TDR based technique and (ii) the consideration of the broadband permittivity spectrum of the porous material. In order to systematic analyze the model, theoretical results were compared with measurements as well as 3D broadband finite element modeling of homogeneous and layered media in the coaxial transmission line cell. Defined standards (Teflon, dry glass beads, de-ionized water) were placed inside the line as the dielectric layers in different configurations. With a Thru Reflect Line calibration (TRL) the influences of connectors and adapters at the coaxial line sample holder were removed. The combination of the full two port calibration procedure and broadband modeling approach turns out to achieve a good accordance of modeling and experimental results. The next step is the implementation of an inversion to calculate the material parameters of every layer out of the s-parameters of the layered sample.

Frequency-Selective Surface to Determine Permittivity of Industrial Oil and Effect of Nanoparticle Addition in X-Band

NASA Astrophysics Data System (ADS)

Jafari, Fereshteh Sadat; Ahmadi-Shokouh, Javad

2018-02-01

A frequency-selective surface (FSS) structure is proposed for characterization of the permittivity of industrial oil using a transmission/reflection (TR) measurement scheme in the X-band. Moreover, a parameter study is presented to distinguish the dielectric constant and loss characteristics of test materials. To model the loss empirically, we used CuO nanoparticles artificially mixed with an industrial oil. In this study, the resonant frequency of the FSS is the basic parameter used to determine the material characteristics, including resonance properties such as the magnitude of transmission ( S 21), bandwidth, and frequency shift. The results reveal that the proposed FSS structure and setup can act well as a sensor for characterization of the dielectric properties of industrial oil.

Dielectric study of aqueous solutions of sodium dodecyl sulfate in the frequency span 20 Hz to 2 MHz

NASA Astrophysics Data System (ADS)

Kadve, A. M.; Vankar, H. P.; Rana, V. A.

2017-05-01

Dielectric measurements were carried out for aqueous solutions of Sodium Dodecyl Sulfate (SDS) in the frequency span of 20 Hz to 2 MHz at 300.15 K temperature using precision LCR meter. Also the refractive indices were measured for the solutions at 300.15 K temperature using Abbe's refractometer. The measurements were done for ten different concentrations of SDS in distilled water. Determined values of complex permittivity as a function of frequency were used to evaluate other parameters like loss tangent and electric modulus for the liquid samples. The permittivity at optical frequency were also calculated from the measured refractive indices for the aqueous solutions. The effect of concentration variation of SDS in the aqueous solutions on the determined parameters is discussed.

New sample cell configuration for wide-frequency dielectric spectroscopy: DC to radio frequencies.

PubMed

Nakanishi, Masahiro; Sasaki, Yasutaka; Nozaki, Ryusuke

2010-12-01

A new configuration for the sample cell to be used in broadband dielectric spectroscopy is presented. A coaxial structure with a parallel plate capacitor (outward parallel plate cell: OPPC) has made it possible to extend the frequency range significantly in comparison with the frequency range of the conventional configuration. In the proposed configuration, stray inductance is significantly decreased; consequently, the upper bound of the frequency range is improved by two orders of magnitude from the upper limit of conventional parallel plate capacitor (1 MHz). Furthermore, the value of capacitance is kept high by using a parallel plate configuration. Therefore, the precision of the capacitance measurement in the lower frequency range remains sufficiently high. Finally, OPPC can cover a wide frequency range (100 Hz-1 GHz) with an appropriate admittance measuring apparatus such as an impedance or network analyzer. The OPPC and the conventional dielectric cell are compared by examining the frequency dependence of the complex permittivity for several polar liquids and polymeric films.

On the correct choice of equivalent circuit for fitting bulk impedance data of ionic/electronic conductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hernández, Miguel A.; Masó, Nahum; West, Anthony R.

Bulk conductivity data of ionically and electronically conducting solid electrolytes and electronic ceramics invariably show a frequency dependence that cannot be modelled by a single-valued resistor. To model this, common practice is to add a constant phase element (CPE) in parallel with the bulk resistance. To fit experimental data on a wide variety of materials, however, it is also essential to include the limiting, high frequency permittivity of the material in the equivalent circuit. Failure to do so can lead to incorrect values for the sample resistance and CPE parameters and to an inappropriate circuit for materials that are electricallymore » heterogeneous.« less

Novel joint TOA/RSSI-based WCE location tracking method without prior knowledge of biological human body tissues.

PubMed

Ito, Takahiro; Anzai, Daisuke; Jianqing Wang

2014-01-01

This paper proposes a novel joint time of arrival (TOA)/received signal strength indicator (RSSI)-based wireless capsule endoscope (WCE) location tracking method without prior knowledge of biological human tissues. Generally, TOA-based localization can achieve much higher localization accuracy than other radio frequency-based localization techniques, whereas wireless signals transmitted from a WCE pass through various kinds of human body tissues, as a result, the propagation velocity inside a human body should be different from one in free space. Because the variation of propagation velocity is mainly affected by the relative permittivity of human body tissues, instead of pre-measurement for the relative permittivity in advance, we simultaneously estimate not only the WCE location but also the relative permittivity information. For this purpose, this paper first derives the relative permittivity estimation model with measured RSSI information. Then, we pay attention to a particle filter algorithm with the TOA-based localization and the RSSI-based relative permittivity estimation. Our computer simulation results demonstrates that the proposed tracking methods with the particle filter can accomplish an excellent localization accuracy of around 2 mm without prior information of the relative permittivity of the human body tissues.

The retrieval of a buried cylindrical obstacle by a constrained modified gradient method in the H-polarization case and for Maxwellian materials

NASA Astrophysics Data System (ADS)

Lambert, M.; Lesselier, D.; Kooij, B. J.

1998-10-01

The retrieval of an unknown, possibly inhomogeneous, penetrable cylindrical obstacle buried entirely in a known homogeneous half-space - the constitutive material parameters of the obstacle and of its embedding obey a Maxwell model - is considered from single- or multiple-frequency aspect-limited data collected by ideal sensors located in air above the embedding half-space, when a small number of time-harmonic transverse electric (TE)-polarized line sources - the magnetic field H is directed along the axis of the cylinder - is also placed in air. The wavefield is modelled from a rigorous H-field domain integral-differential formulation which involves the dot product of the gradients of the single component of H and of the Green function of the stratified environment times a scalar-valued contrast function which contains the obstacle parameters (the frequency-independent, position-dependent relative permittivity and conductivity). A modified gradient method is developed in order to reconstruct the maps of such parameters within a prescribed search domain from the iterative minimization of a cost functional which incorporates both the error in reproducing the data and the error on the field built inside this domain. Non-physical values are excluded and convergence reached by incorporating in the solution algorithm, from a proper choice of unknowns, the condition that the relative permittivity be larger than or equal to 1, and the conductivity be non-negative. The efficiency of the constrained method is illustrated from noiseless and noisy synthetic data acquired independently. The importance of the choice of the initial values of the sought quantities, the need for a periodic refreshment of the constitutive parameters to avoid the algorithm providing inconsistent results, and the interest of a frequency-hopping strategy to obtain finer and finer features of the obstacle when the frequency is raised, are underlined. It is also shown that though either the permittivity map or the conductivity map can be obtained for a fair variety of cases, retrieving both of them may be difficult unless further information is made available.

Gain assisted nanocomposite multilayers with near zero permittivity modulus at visible frequencies

NASA Astrophysics Data System (ADS)

Rizza, Carlo; Di Falco, Andrea; Ciattoni, Alessandro

2011-11-01

We have fabricated a nano-laminate by alternating metal and gain medium layers, the gain dielectric consisting of a polymer incorporating optically pumped dye molecules. From standard reflection-transmission experiments, we show that, at a visible wavelength, both the real and the imaginary parts of the permittivity ɛ∥ attain very small values and we measure, at λ = 604 nm, |ɛ∥|=0.04 which is 21.5% smaller than its value in the absence of optical pumping. Our investigation thus proves that a medium with a permittivity with very small modulus, a key condition promising efficient subwavelength optical steering, can be actually synthesized.

Large enhanced dielectric permittivity in polyaniline passivated core-shell nano magnetic iron oxide by plasma polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joy, Lija K.; Sooraj, V.; Sethulakshmi, N.

2014-03-24

Commercial samples of Magnetite with size ranging from 25–30 nm were coated with polyaniline by using radio frequency plasma polymerization to achieve a core shell structure of magnetic nanoparticle (core)–Polyaniline (shell). High resolution transmission electron microscopy images confirm the core shell architecture of polyaniline coated iron oxide. The dielectric properties of the material were studied before and after plasma treatment. The polymer coated magnetite particles exhibited a large dielectric permittivity with respect to uncoated samples. The dielectric behavior was modeled using a Maxwell–Wagner capacitor model. A plausible mechanism for the enhancement of dielectric permittivity is proposed.

Enhanced dielectric performance of three phase percolative composites based on thermoplastic-ceramic composites and surface modified carbon nanotube

NASA Astrophysics Data System (ADS)

Yang, Yang; Sun, Haoliang; Zhu, Benpeng; Wang, Ziyu; Wei, Jianhong; Xiong, Rui; Shi, Jing; Liu, Zhengyou; Lei, Qingquan

2015-01-01

Three-phase composites were prepared by embedding CaCu3Ti4O12(CCTO) nanoparticles and Multiwalled Carbon Nanotube (MWNT) into polyimide (PI) matrix via in-situ polymerization. The dependences of electric and dielectric properties of the resultant composites on volume fractions of filler and frequency were investigated. The dielectric permittivity of PI/CCTO-surface modified MWNT (MWNT-S) composite reached as high as 252 at 100 Hz at 0.1 vol. % filler (MWNT-S), which is about 63 times higher than that of pure PI. Also the dielectric loss is only 0.02 at 100 Hz. The results are in good agreement with the percolation theory. It is shown that embedding high aspect ratio MWNT-S in PI/CCTO composites is an effective means to enhance the dielectric permittivity and reduce the percolation threshold. The dielectric properties of the composites will meet the practical requirements for the application in high dielectric constant capacitors and high energy density materials.

Capsize of polarization in dilute photonic crystals.

PubMed

Gevorkian, Zhyrair; Hakhoumian, Arsen; Gasparian, Vladimir; Cuevas, Emilio

2017-11-29

We investigate, experimentally and theoretically, polarization rotation effects in dilute photonic crystals with transverse permittivity inhomogeneity perpendicular to the traveling direction of waves. A capsize, namely a drastic change of polarization to the perpendicular direction is observed in a one-dimensional photonic crystal in the frequency range 10 ÷ 140 GHz. To gain more insights into the rotational mechanism, we have developed a theoretical model of dilute photonic crystal, based on Maxwell's equations with a spatially dependent two dimensional inhomogeneous dielectric permittivity. We show that the polarization's rotation can be explained by an optical splitting parameter appearing naturally in Maxwell's equations for magnetic or electric fields components. This parameter is an optical analogous of Rashba like spin-orbit interaction parameter present in quantum waves, introduces a correction to the band structure of the two-dimensional Bloch states, creates the dynamical phase shift between the waves propagating in the orthogonal directions and finally leads to capsizing of the initial polarization. Excellent agreement between theory and experiment is found.

An anisotropic lens for transitioning plane waves between media of different permittivities

NASA Astrophysics Data System (ADS)

Stone, Alexander P.; Baum, Carl E.

1988-11-01

A particularly simple geometry is considered in which an inhomogeneous and anisotropic lens is specified for the transition of plane waves between media of different permittivities. The permittivities of the regions outside of the lens can be constant, but the permittivity of the lens region depends on position. Results are presented for a plane wave in the second medium propagating normally to the assumed plane boundary of that medium. The results for the case of normal incidence are then generalized to the case of nonnormal incidence. The conditions of transit time conservation and impedance matching are related to the Brewster angle.

Time-dependent entropy evolution in microscopic and macroscopic electromagnetic relaxation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baker-Jarvis, James

This paper is a study of entropy and its evolution in the time and frequency domains upon application of electromagnetic fields to materials. An understanding of entropy and its evolution in electromagnetic interactions bridges the boundaries between electromagnetism and thermodynamics. The approach used here is a Liouville-based statistical-mechanical theory. I show that the microscopic entropy is reversible and the macroscopic entropy satisfies an H theorem. The spectral entropy development can be very useful for studying the frequency response of materials. Using a projection-operator based nonequilibrium entropy, different equations are derived for the entropy and entropy production and are applied tomore » the polarization, magnetization, and macroscopic fields. I begin by proving an exact H theorem for the entropy, progress to application of time-dependent entropy in electromagnetics, and then apply the theory to relevant applications in electromagnetics. The paper concludes with a discussion of the relationship of the frequency-domain form of the entropy to the permittivity, permeability, and impedance.« less

The microwave properties of Ag(Ta0.8Nb0.2)O3 thick film interdigital capacitors on alumina substrates

NASA Astrophysics Data System (ADS)

Lee, Ku-Tak; Koh, Jung-Hyuk

2012-01-01

In this paper, we will introduce the microwave properties of Ag(Ta0.8Nb0.2)O3 thick film planar type interdigital capacitors fabricated on alumina substrates. The tailored paraelectric state of Ag(Ta,Nb)O3 allows the material to be regarded as a part of the family of microwave materials. As thick films formed in our experiment, Ag(Ta,Nb)O3 exhibited extremely low dielectric loss with relatively high dielectric permittivity. This low dielectric loss is a very important issue for microwave applications. Therefore, we investigated the microwave properties of Ag(Ta0.8Nb0.2)O3 thick film planar type interdigital capacitors. Ag(Ta0.8Nb0.2)O3 thick films were prepared by a screen-printing method on alumina substrates and were sintered at 1140 °C for 2 hrs. The XRD analysis results showed that the Ag(Ta0.8Nb0.2)O3 thick film has the perovskite structure. The frequency dependent dielectric permittivity showed that these Ag(Ta0.8Nb0.2)O3 thick film planar type interdigital capacitors have very weak frequency dispersions with low loss tangents in the microwave range.

Reconfigurable all-dielectric metasurface based on tunable chemical systems in aqueous solution.

PubMed

Yang, Xiaoqing; Zhang, Di; Wu, Shiyue; Yin, Yang; Li, Lanshuo; Cao, Kaiyuan; Huang, Kama

2017-06-09

Dynamic control transmission and polarization properties of electromagnetic (EM) wave propagation is investigated using chemical reconfigurable all-dielectric metasurface. The metasurface is composed of cross-shaped periodical teflon tubes and inner filled chemical systems (i.e., mixtures and chemical reaction) in aqueous solution. By tuning the complex permittivity of chemical systems, the reconfigurable metasurface can be easily achieved. The transmission properties of different incident polarized waves (i.e., linear and circular polarization) were simulated and experimentally measured for static ethanol solution as volume ratio changed. Both results indicated this metasurface can serve as either tunable FSS (Frequency Selective Surface) or tunable linear-to-circular/cross Polarization Converter at required frequency range. Based on the reconfigurable laws obtained from static solutions, we developed a dynamic dielectric system and researched a typical chemical reaction with time-varying permittivity filled in the tubes experimentally. It provides new ways for realizing automatic reconfiguration of metasurface by chemical reaction system with given variation laws of permittivity.

Colossal dielectric permittivity in (Al + Nb) co-doped rutile SnO2 ceramics with low loss at room temperature

NASA Astrophysics Data System (ADS)

Song, Yongli; Wang, Xianjie; Zhang, Xingquan; Qi, Xudong; Liu, Zhiguo; Zhang, Lingli; Zhang, Yu; Wang, Yang; Sui, Yu; Song, Bo

2016-10-01

The exploration of colossal dielectric permittivity (CP) materials with low dielectric loss in a wide range of frequencies/temperatures continues to attract considerable interest. In this paper, we report CP in (Al + Nb) co-doped rutile SnO2 ceramics with a low dielectric loss at room temperature. Al0.02Nb0.05Sn0.93O2 and Al0.03Nb0.05Sn0.92O2 ceramics exhibit high relative dielectric permittivities (above 103) and low dielectric losses (0.015 < tan δ < 0.1) in a wide range of frequencies and at temperatures from 140 to 400 K. Al doping can effectively modulate the dielectric behavior by increasing the grain and grain boundary resistances. The large differences in the resistance and conductive activation energy of the grains and grain boundaries suggest that the CP in co-doped SnO2 ceramics can be attributed to the internal barrier layer capacitor effect.

Electromagnetic Wave Transmittance Control using Anisotropic Plasma Lattice

NASA Astrophysics Data System (ADS)

Matlis, Eric; Corke, Thomas; Hoffman, Anthony

2017-11-01

Experiments of transmission through a lattice array of plasma columns have shown an absorption band close to the plasma frequency at 14 GHz. The beam was oriented at a 35° incident angle to the planar plasma cell. These experiments were designed to determine if the observed absorption was the result of the isotropic plasma medium or that of an anisotropic metamaterial. Transmission of the microwave energy was not consistent with an isotropic material in which absorption would monotonically increase below the plasma frequency. The experimental results are supported by an anisotropic model which was developed for the plasma permittivity using an effective medium approximation. The plasma columns were modeled as uniform rods with permittivity described by a Drude model while the components of the permittivity tensor was calculated using the Maxwell-Garnett effective medium theory. Electron densities of n = 4 x1012 cm-3 were assumed which is consistent with prior experimental measurements. This model confirms the existence of non-zero imaginary wave vector k in a narrow region centered about 14 GHz.

Colossal permittivity and the polarization mechanism of (Mg, Mn) co-doped LaGaO3 ceramics

NASA Astrophysics Data System (ADS)

Luo, Tingting; Liu, Zhifu; Zhang, Faqiang; Li, Yongxiang

2018-03-01

Mg and Mn co-doped LaGa0.7-xMgxMn0.3O3 (x = 0, 0.05, 0.10, 0.15) ceramics were prepared by a solid-state reaction method. The electrical properties of the LaGa0.7-xMgxMn0.3O3 ceramics were studied in detail by dielectric spectra, impedance spectra, and I-V characteristic analysis. Colossal permittivity up to 104 could be obtained across the frequency range up to 104 Hz. The impedance analysis of the co-doped LaGaO3 ceramics indicated that the Mott's variable range hopping (VRH) polarization should be the main origin of colossal permittivity. Mg and Mn co-doping suppressed the formation of Mn3+ and enhanced the VRH polarization, resulting in increased permittivity. Partial localization of electrons by Mg reduced the long-range electron hopping and led to the decrease in dielectric loss.

Electrophysical properties of water and ice under isentropic compression to megabar pressures

NASA Astrophysics Data System (ADS)

Belov, S. I.; Boriskov, G. V.; Bykov, A. I.; Dolotenko, M. I.; Egorov, N. I.; Korshunov, A. S.; Kudasov, Yu. B.; Makarov, I. V.; Selemir, V. D.; Filippov, A. V.

2017-02-01

The relative permittivity and specific conductivity of water and ice are measured under isentropic compression to pressures above 300 GPa. Compression is initiated by a pulse of an ultrahigh magnetic field generated by an MK-1 magnetocumulative generator. The sample is placed in a coaxial compression chamber with an initial volume of about 40 cm3. The complex relative permittivity was measured by a fast-response reflectometer at a frequency of about 50 MHz. At the compression of water, its relative permittivity increases to ɛ = 350 at a pressure of 8 GPa, then drops sharply to ɛ = 140, and further decreases smoothly. It is shown that measurements of the relative permittivity under isentropic compression make it possible to determine interfaces between ordered and disordered phases of water and ice, as well as to reveal features associated with a change in the activation energy of defects.

A microcontroller-based microwave free-space measurement system for permittivity determination of lossy liquid materials.

PubMed

Hasar, U C

2009-05-01

A microcontroller-based noncontact and nondestructive microwave free-space measurement system for real-time and dynamic determination of complex permittivity of lossy liquid materials has been proposed. The system is comprised of two main sections--microwave and electronic. While the microwave section provides for measuring only the amplitudes of reflection coefficients, the electronic section processes these data and determines the complex permittivity using a general purpose microcontroller. The proposed method eliminates elaborate liquid sample holder preparation and only requires microwave components to perform reflection measurements from one side of the holder. In addition, it explicitly determines the permittivity of lossy liquid samples from reflection measurements at different frequencies without any knowledge on sample thickness. In order to reduce systematic errors in the system, we propose a simple calibration technique, which employs simple and readily available standards. The measurement system can be a good candidate for industrial-based applications.

Effect of ion concentration, solution and membrane permittivity on electric energy storage and capacitance.

PubMed

Tajparast, Mohammad; Glavinović, Mladen I

2018-06-06

Bio-membranes as capacitors store electric energy, but their permittivity is low whereas the permittivity of surrounding solution is high. To evaluate the effective capacitance of the membrane/solution system and determine the electric energy stored within the membrane and in the solution, we estimated their electric variables using Poisson-Nernst-Planck simulations. We calculated membrane and solution capacitances from stored electric energy. The effective capacitance was calculated by fitting a six-capacitance model to charges (fixed and ion) and associated potentials, because it cannot be considered as a result of membrane and solution capacitance in series. The electric energy stored within the membrane (typically much smaller than that in the solution), depends on the membrane permittivity, but also on the external electric field, surface charge density, water permittivity and ion concentration. The effect on capacitances is more specific. Solution capacitance rises with greater solution permittivity or ion concentration, but the membrane capacitance (much smaller than solution capacitance) is only influenced by its permittivity. Interestingly, the effective capacitance is independent of membrane or solution permittivity, but rises as the ion concentration increases and surface charge becomes positive. Experimental estimates of membrane capacitance are thus not necessarily a reliable index of its surface area. Copyright © 2018. Published by Elsevier B.V.

Properties of dielectric dead layers for SrTiO3 thin films on Pt electrodes

NASA Astrophysics Data System (ADS)

Finstrom, Nicholas H.; Cagnon, Joel; Stemmer, Susanne

2007-02-01

Dielectric measurements as a function of temperature were used to characterize the properties of the dielectric dead layers in parallel-plate capacitors with differently textured SrTiO3 thin films and Pt electrodes. The apparent thickness dependence of the permittivity was described with low-permittivity passive (dead) layers at the interfaces connected in series with the bulk of the SrTiO3 film. Interfacial capacitance densities changed with the film microstructure and were weakly temperature dependent. Estimates of the dielectric dead layer thickness and permittivity were limited by the film surface roughness (˜5nm ). The consequences for the possible origins of dielectric dead layers that have been proposed in the literature are discussed.

Dielectric spectroscopy in aqueous solutions of paracetamol over the frequency range of 20 Hz to 2 MHz at 293.15 K temperature

NASA Astrophysics Data System (ADS)

Pandit, T. R.; Rana, V. A.

2018-05-01

Frequency domain dielectric relaxation spectroscopy plays an important role in the study of pharmaceutical drug molecules. The complex relative dielectric permittivity ɛ*(ω) = ɛ' - j ɛ" of aqueous solutions of paracetamol in the frequency range of 20 Hz to 2 MHz at a temperature range of 293.15 K are measured with the help of Agilent precision LCR meter E4980A along with four terminal liquid test fixture Agilent 16452A. Data of complex relative permittivity are used to calculate loss tangent for all concentrations of paracetamol in distilled water. Electrode polarization relaxation time has been calculated for all solutions. Effect of variation of concentrations of paracetamol in distilled water on these dielectric parameters is discussed.

Dielectric and relaxation properties of poly(o-anisidine)/graphene nanocomposite

NASA Astrophysics Data System (ADS)

Sangamithirai, D.; Narayanan, V.; Stephen, A.

2016-05-01

Poly(o-anisidine)/graphene (POA/GR) nanocomposite was synthesized via chemical oxidative polymerization of o-anisidine in the presence of graphene sheets in acidic medium. The electrical properties of the nanocomposite are studied using AC impedance spectroscopic technique. It has been found that the room temperature electrical conductivity value enhanced from 1.28 × 10-6 S cm-1 to 4.47 × 10-4 S cm-1 on addition of 10 wt % of graphene into the polymer. An analysis of real and imaginary parts of dielectric permittivity reveals that both ɛ` and ɛ״ increases with the decrease of frequency at all temperature levels. Frequency dependence of dielectric loss (tan δ) spectrum indicates that hopping frequency increases with temperature and the relaxation time decreases from 2.67 × 10-5 to 7.28 × 10-6 sec.

Optical properties of antiferromagnetic/ion-crystal superlattices

NASA Astrophysics Data System (ADS)

Ta, Jin-Xing; Song, Yu-Ling; Wang, Xuan-Zhang

2012-01-01

Transmission, refraction and absorption properties of an antiferromagnetic/ion-crystal superlattice are investigated. The transmission spectra based on FeF2/TlBr superlattices reveal that there exist two intriguing guided modes in a wide stop band. Additionally, FeF2/TlBr superlattices possess either the negative refraction or the quasi left-handedness, or even simultaneously hold them at certain frequencies of two guided modes, which require both negative magnetic permeability of antiferromagnetic layers and negative permittivity of ion-crystal layers. Frequency regimes of the guided modes will be dependent on the magnitude of the external magnetic field. Therefore, handedness and refraction properties of the system can be manipulated by modifying the external magnetic field. Absorption spectra exhibit that absorption corresponding to guided modes is noticeable.

Numerical calculations for effects of structure of skeletal muscle on frequency-dependence of its electrical admittance and impedance

NASA Astrophysics Data System (ADS)

Sekine, Katsuhisa; Yamada, Ayumi; Kageyama, Hitomi; Igarashi, Takahiro; Yamamoto, Nana; Asami, Koji

2015-06-01

Numerical calculations were carried out by the finite difference method using three-dimensional models to examine effects of the structure of skeletal muscle on the frequency-dependence of its electrical admittance Y and impedance Z in transversal and longitudinal directions. In the models, the muscle cell was represented by a rectangular solid surrounded by a smooth surface membrane, and the cells were assumed to be distributed periodically. The width of the cross section of the cell, thickness of the intercellular medium, and the relative permittivities and the conductivities of the cell interior, the intercellular medium and the surface membrane were changed. Based on the results of the calculations, reported changes in Y and Z of the muscles from 1 kHz to 1 MHz were analyzed. The analyses revealed that a decreased cell radius was reasonable to explain the Y and Z of the muscles of immature rats, rats subjected to sciatic nerve crush at chronic stage and the amyotrophic lateral sclerosis (ALS) mice. Changes in Y and Z due to the sciatic nerve crush at acute stage were attributable to the decreased cell radius, the increased space between the cells, the increased permittivity of the surface membrane and the increased conductivity of the cell interior. The changes in Z due to contraction were explained by the changes in the cell radius, and the conductivities of the cell interior and the intercellular medium. The changes in Z of meat due to aging were compared with the effects of the increase in the conductivity of the surface membrane.

A complex permittivity model for field estimation of soil water contents using time domain reflectometry

USDA-ARS?s Scientific Manuscript database

Accurate electromagnetic sensing of soil water contents (') under field conditions is complicated by the dependence of permittivity on specific surface area, temperature, and apparent electrical conductivity, all which may vary across space or time. We present a physically-based mixing model to pred...

The effects of magnetic fields exposure on relative permittivity of saline solutions measured by a high resolution SPR system

PubMed Central

Jiang, Li; Zhao, Xinyuan; Fei, Yue; Yu, Dongdong; Qian, Jun; Tong, Jinguang; Chen, Guangdi; He, Sailing

2016-01-01

A measurement system for the relative permittivity of a physiological solution under 50 Hz magnetic fields (MF) is presented. It is based on a phase-sensitive surface plasmon resonance (SPR) system. Relative permittivity was analyzed for different solute concentrations of sodium chloride under various MF exposure parameters. We found that MF exposure at 0.2–4.0 mT step-wise decreased significantly the SPR phase signal of a 0.9% sodium chloride solution while 0.1 mT of MF exposure did not. The decreases in the SPR phase signal depended on the duration of MF exposure, and the signal reached a plateau after 15 min of exposure. Interestingly, the decreased SPR phase signal showed a gradual increase and approached the background level when the exposure was drawn off. In addition, we found that the response of the sodium chloride solution to MF also depended on its concentration. In brief, the relative permittivity of sodium chloride in solutions appears to be practically affected by 50 Hz MF exposure. Our data indicates that the relative permittivity of the saline solution influenced by MF exposure should be considered when investigating the biological effects of MF exposure on organisms in experimental study. PMID:27121618

Ionic conductivity and dielectric permittivity of polymer electrolyte plasticized with polyethylene glycol

NASA Astrophysics Data System (ADS)

Das, S.; Ghosh, A.

2016-05-01

We have studied ionic conductivity and dielectric permittivity of PEO-LiClO4 solid polymer electrolyte plasticized with polyethylene glycol (PEG). The temperature dependence of the ionic conductivity has been well interpreted using Vogel-Tamman-Fulcher equation. The maximum dielectric constant is observed for 30 wt. % of PEG content. To get further insights into the ion dynamics, the complex dielectric permittivity has been studied with Havriliak-Negami function. The variation of relaxation time with inverse temperature obtained from HN formalism follows VTF nature.

Percolation-induced plasmonic state and double negative electromagnetic properties of Ni-Zn Ferrite/Cu granular composite materials

NASA Astrophysics Data System (ADS)

Massango, Herieta; Kono, Koji; Tsutaoka, Takanori; Kasagi, Teruhiro; Yamamoto, Shinichiro; Hatakeyama, Kenichi

2018-05-01

Complex permeability and permittivity spectra of Ni-Zn Ferrite/Cu hybrid granular composite materials have been studied in the RF to microwave frequency range. The electrical conductivity σ shows insulating properties in the volume fraction of Cu particles below φ = 0.14. A large jump in conductivity was observed between φ = 0.14 and 0.24 indicating that the Cu particles make metallic conduction between this interval. Hence, the percolation threshold φC, was estimated to be 0.14. A percolation-induced low frequency plasmonic state with negative permittivity spectrum was observed from φ = 0.14-0.24. Meanwhile the negative permeability was observed at φ = 0.16, 0.19 and 0.24. Hence the DNG characteristic was realized in these Cu volume content in the frequency range from 105 MHz to 2 GHz.

Determination of medium electrical properties through full-wave modelling of frequency domain reflectrometry data

NASA Astrophysics Data System (ADS)

André, Frédéric; Lambot, Sébastien

2015-04-01

Accurate knowledge of the shallow soil properties is of prime importance in agricultural, hydrological and environmental engineering. During the last decade, numerous geophysical techniques, either invasive or resorting to proximal or remote sensing, have been developed and applied for quantitative characterization of soil properties. Amongst them, time domain reflectrometry (TDR) and frequency domain reflectometry (FDR) are recognized as standard techniques for the determination of soil dielectric permittivity and electrical conductivity, based on the reflected electromagnetic waves from a probe inserted into the soil. TDR data were first commonly analyzed in the time domain using methods considering only a part of the waveform information. Later, advancements have led to the possibility of analyzing the TDR signal through full-wave inverse modeling either in the time or the frequency domains. A major advantage of FDR compared to TDR is the possibility to increase the bandwidth, thereby increasing the information content of the data and providing more detailed characterization of the medium. Amongst the recent works in this field, Minet et al. (2010) developed a modeling procedure for processing FDR data based on an exact solution of Maxwell's equations for wave propagation in one-dimensional multilayered media. In this approach, the probe head is decoupled from the medium and is fully described by characteristic transfer functions. The authors successfully validated the method for homogeneous sand subject to a range of water contents. In the present study, we further validated the modelling approach using reference liquids with well-characterized frequency-dependent electrical properties. In addition, the FDR model was coupled with a dielectric mixing model to investigate the ability of retrieving water content, pore water electrical conductivity and sand porosity from inversion of FDR data acquired in sand subject to different water content levels. Finally, the possibility of reconstructing the vertical profile of the properties by inversion of FDR data collected during progressive insertion of the probe into a vertically heterogeneous medium was also investigated. Index Terms: Frequency domain reflectrometry (FDR), frequency dependence, dielectric permittivity, electrical conductivity Reference: Minet J., Lambot S., Delaide G., Huisman J.A., Vereecken H., Vanclooster M., 2010. A generalized frequency domain reflectometry modeling technique for soil electrical properties determination. Vadose Zone Journal, 9: 1063-1072.

Metamaterials and the Landau–Lifshitz permeability argument: Large permittivity begets high-frequency magnetism

PubMed Central

Merlin, Roberto

2009-01-01

Homogeneous composites, or metamaterials, made of dielectric or metallic particles are known to show magnetic properties that contradict arguments by Landau and Lifshitz [Landau LD, Lifshitz EM (1960) Electrodynamics of Continuous Media (Pergamon, Oxford, UK), p 251], indicating that the magnetization and, thus, the permeability, loses its meaning at relatively low frequencies. Here, we show that these arguments do not apply to composites made of substances with ImεS ≫ λ/ℓ or ReεS ∼ λ/ℓ (εS and ℓ are the complex permittivity and the characteristic length of the particles, and λ ≫ ℓ is the vacuum wavelength). Our general analysis is supported by studies of split rings, one of the most common constituents of electromagnetic metamaterials, and spherical inclusions. An analytical solution is given to the problem of scattering by a small and thin split ring of arbitrary permittivity. Results reveal a close relationship between εS and the dynamic magnetic properties of metamaterials. For |εS | ≪ λ/a (a is the ring cross-sectional radius), the composites exhibit very weak magnetic activity, consistent with the Landau–Lifshitz argument and similar to that of molecular crystals. In contrast, large values of the permittivity lead to strong diamagnetic or paramagnetic behavior characterized by susceptibilities whose magnitude is significantly larger than that of natural substances. We compiled from the literature a list of materials that show high permittivity at wavelengths in the range 0.3–3000 μm. Calculations for a system of spherical inclusions made of these materials, using the magnetic counterpart to Lorentz–Lorenz formula, uncover large magnetic effects the strength of which diminishes with decreasing wavelength. PMID:19188589

Spectral characterization of dielectric materials using terahertz measurement systems

NASA Astrophysics Data System (ADS)

Seligman, Jeffrey M.

The performance of modern high frequency components and electronic systems are often limited by the properties of the materials from which they are made. Over the past decade, there has been an increased emphasis on the development of new, high performance dielectrics for use in high frequency systems. The development of these materials requires novel broadband characterization, instrumentation, and extraction techniques, from which models can be formulated. For this project several types of dielectric sheets were characterized at terahertz (THz) frequencies using quasi-optical (free-space) techniques. These measurement systems included a Fourier Transform Spectrometer (FTS, scalar), a Time Domain Spectrometer (TDS, vector), a Scalar Network Analyzer (SNA), and a THz Vector Network Analyzer (VNA). Using these instruments the THz spectral characteristics of dielectric samples were obtained. Polarization based anisotropy was observed in many of the materials measured using vector systems. The TDS was the most informative and flexible instrument for dielectric characterization at THz frequencies. To our knowledge, this is the first such comprehensive study to be performed. Anisotropy effects within materials that do not come into play at microwave frequencies (e.g. ~10 GHz) were found, in many cases, to increase measured losses at THz frequencies by up to an order of magnitude. The frequency dependent properties obtained during the course of this study included loss tangent, permittivity (index of refraction), and dielectric constant. The results were largely consistent between all the different systems and correlated closely to manufacturer specifications over a wide frequency range (325 GHz-1.5 THz). Anisotropic behavior was observed for some of the materials. Non-destructive evaluation and testing (NDE/NDT) techniques were used throughout. A precision test fixture was developed to accomplish these measurements. Time delay, insertion loss, and S-parameters were measured directly, from which loss tangent, index of refraction, and permittivity was extracted. The test materials were low-loss dielectric slabs ranging in thickness from 1-60 mils. The substrate sheets were PTFE, fiberglass, and epoxy-ceramic composite substrates. The other group was polyethylene plastic sheets (LDPE/HDPE/UMHW) and 3D printer Photopolymers. The results were verified by using several online THz spectral databases and compared to manufacturer data sheets. Permittivity and loss of some of the test samples varied as a function of polarization angle. 0 - 90 degrees of rotation were tested (i.e., H-V, and 45 degrees polarization). Inter-molecular scattering in the composite materials raised the loss considerably. This effect was verified. Standard, well documented, material types were selected for the project for best comparison. These techniques can also be applied to analyze newer substances such as nanodielectrics.

Vegetation dielectric characterization using an open-ended coaxial probe

NASA Astrophysics Data System (ADS)

Mavrovic, A.; Roy, A.; Royer, A.; Boone, F.; Pappas, C.; Filali, B.

2017-12-01

The detection of freeze/thaw (F/T) physical state of soil is one of the main objectives of the SMAP mission as well as one of the secondary objectives of the SMOS mission. Annual F/T cycles have substantial impacts on surface energy budgets, permafrost conditions, as well as forest water and carbon dynamics. It has been shown that spaceborne L-band passive radiometry is a promising tool to monitor F/T due to the substantial differences between the permittivity of water and ice at these frequencies. However, the decoupling of the signal between soil and vegetation components remains challenging for all microwave remote sensing applications at various spatial scales. Radiative transfer models in the microwave domain are generally poorly parameterized to consider the non-negligible contribution of vegetation. The main objective of this research is to assess the skill of a recently developed Open-Ended Coaxial Probe (OECP) to measure the complex microwave permittivity of vegetation and soils and to derive a relation between the impact of vegetation on the microwave signal and the vegetation permittivity that could serve as a validation tool for soil models especially in frozen state. Results show that the OECP is a suitable tool to infer the radial profile of the complex permittivity in L-band of trees. A clear distinction can be made between the dielectric characterization of the sapwood where the permittivity is high because of the high permittivity of water but decrease with depth, and the heartwood where the permittivity is low and relatively constant. The seasonal cycle of the F/T state of the vegetation can also be observed since it is strongly correlated with the permittivity of the wood. The permittivity of a tree over the winter season is very low and homogenous since the permittivity of ice is significantly lower than water and the sap flow is negligible. The fluctuation of the frozen and thawed permittivity for different tree species was evaluated, focusing on four widespread boreal tree species. Future work will focus on observing the effect of the tree permittivity on the vegetation emission and brightness temperature (Tb) and to upscale that information for satellite-borne passive microwave observations and global monitoring of freeze/thaw and soil moisture.

Colossal permittivity behavior and its origin in rutile (Mg1/3Ta2/3)xTi1-xO2.

PubMed

Dong, Wen; Chen, Dehong; Hu, Wanbiao; Frankcombe, Terry J; Chen, Hua; Zhou, Chao; Fu, Zhenxiao; Wei, Xiaoyong; Xu, Zhuo; Liu, Zhifu; Li, Yongxiang; Liu, Yun

2017-08-30

This work investigates the synthesis, chemical composition, defect structures and associated dielectric properties of (Mg 2+ , Ta 5+ ) co-doped rutile TiO 2 polycrystalline ceramics with nominal compositions of (Mg 2+ 1/3 Ta 5+ 2/3 ) x Ti 1-x O 2 . Colossal permittivity (>7000) with a low dielectric loss (e.g. 0.002 at 1 kHz) across a broad frequency/temperature range can be achieved at x = 0.5% after careful optimization of process conditions. Both experimental and theoretical evidence indicates such a colossal permittivity and low dielectric loss intrinsically originate from the intragrain polarization that links to the electron-pinned [Formula: see text] defect clusters with a specific configuration, different from the defect cluster form previously reported in tri-/pent-valent ion co-doped rutile TiO 2 . This work extends the research on colossal permittivity and defect formation to bi-/penta-valent ion co-doped rutile TiO 2 and elucidates a likely defect cluster model for this system. We therefore believe these results will benefit further development of colossal permittivity materials and advance the understanding of defect chemistry in solids.

Role of defects and oxygen vacancies on dielectric and magnetic properties of Pb2+ ion doped LaFeO3 polycrystalline ceramics

NASA Astrophysics Data System (ADS)

Devi Chandrasekhar, K.; Mallesh, S.; Krishna Murthy, J.; Das, A. K.; Venimadhav, A.

2014-09-01

We have presented the dielectric/impedance spectroscopy of La1-xPbxFeO3 (x=0.15 and 0.25) polycrystalline samples in a wide temperature and frequency range. They exhibited colossal dielectric permittivity and multiple relaxations. Temperature and field dependent magnetization study showed enhancement of magnetization upon Pb doping which has been ascribed to the defect driven magnetization phenomenon. Overall we have emphasized the formation of various kinds of defects and their influence on dielectric and magnetic properties in the system.

Investigation of thermal denaturation of solid oxytocin by terahertz dielectric spectroscopy

NASA Astrophysics Data System (ADS)

Li, Xiangjun; Yang, Xiaojie; Liu, Jianjun; Du, Yong; Hong, Zhi

2014-07-01

We investigate the thermal denaturation of solid oxytocin using terahertz time domain spectroscopy(THz-TDS). When the peptide is heated up from 25°C to 107°C and cooled down to 25°C again, an irreversible decrease in its THz absorption coefficient and refractive index is observed. The corresponding frequency-dependent permittivity during heating is fitted by the Debye model with single relaxation time. The relaxation times during temperature rising agree very well with Arrhenius equation with the activation energy of 3.12kJ/(K•mol) as an indicator for its thermal denaturation difficulty.

Properties of Silica-Based Aerogel Substrates and Application to C-Band Circular Patch Antenna

NASA Astrophysics Data System (ADS)

Abdel-Rahman, Mohamed; Haraz, Osama M.; Ashraf, Nadeem; Zia, Muhammad Fakhar; Khaled, Usama; Elsahfiey, Ibrahim; Alshebeili, Saleh; Sebak, Abdel Razik

2018-03-01

Silica aerogel is a lightweight and low-permittivity dielectric material that possesses attractive features for use as an antenna substrate. In this paper, we characterize the radio frequency and microwave dielectric permittivity properties of substrates composed of silica aerogel encapsulated in polymer aerogel in the frequency range from 10 MHz to 8.5 GHz. Characterized silica-based aerogel substrates show relative permittivity values varying between 1.055 and 1.25 and loss tangent values ranging from 5.08 × 10-4 to 0.0206. Silica-based aerogel substrates thus have the potential of use in designing antennas with high gain and large bandwidth. Validation is presented by characterizing the performance of a manufactured C-band circular patch antenna on silica-based aerogel substrate. The performance is also compared to a design that uses Rogers Duroid RT5880 substrate. The results reveal that the silica aerogel substrate antenna at 7.2 GHz provides 1.5 dB increase in gain, 88% enhancement in bandwidth and 68.5% reduction in mass, in comparison with the antenna on RT5880 substrate.

The measurement of the dielectric constant of concrete pipes and clay pipes

NASA Astrophysics Data System (ADS)

McGraw, David

To optimize the effectiveness of the rehabilitation of underground utilities, taking in consideration limitation of available resources, there is a need for a cost effective and efficient sensing systems capable of providing effective, in real time and in situ, measurement of infrastructural characteristics. To carry out accurate non-destructive condition assessment of buried and above ground infrastructure such as sewers, bridges, pavements and dams, an advanced ultra-wideband (UWB) based radar was developed at Trenchless Technology Centre (TTC) and Centre for Applied Physics Studies (CAPS) at Louisiana Tech University (LTU). One of the major issues in designing the FCC compliant UWB radar was the contribution of the pipe wall, presence of complex soil types and moderate-to-high moisture levels on penetration depth of the electromagnetic (EM) energy. The electrical properties of the materials involved in designing the UWB radar exhibit a significant variation as a result of the moisture content, mineral content, bulk density, temperature and frequency of the electromagnetic signal propagating through it. Since no measurements of frequency dependence of the dielectric permittivity and conductivities of the pipe wall material in the FCC approved frequency range exist, in this thesis, the dielectric constant of concrete and clay pipes are measured over a microwave frequency range from 1 Ghz to 10 Ghz including the effects of moisture and chloride content. A high performance software package called MU-EPSLN(TM) was used for the calculations. Data reduction routines to calculate the complex permeability and permittivity of materials as well as other parameters are also provided. The results obtained in this work will be used to improve the accuracy of the numerical simulations and the performances of the UWB radar system.

Origin of colossal permittivity in (In1/2Nb1/2)TiO2via broadband dielectric spectroscopy.

PubMed

Zhao, Xiao-gang; Liu, Peng; Song, Yue-Chan; Zhang, An-ping; Chen, Xiao-ming; Zhou, Jian-ping

2015-09-21

(In1/2Nb1/2)TiO2 (IN-T) ceramics were prepared via a solid-state reaction route. X-ray diffraction (XRD) and Raman spectroscopy were used for the structural and compositional characterization of the synthesized compounds. The results indicated that the sintered ceramics have a single phase of rutile TiO2. Dielectric spectroscopy (frequency range from 20 Hz to 1 MHz and temperature range from 10 K to 270 K) was performed on these ceramics. The IN-T ceramics showed extremely high permittivities of up to ∼10(3), which can be referred to as colossal permittivity, with relatively low dielectric losses of ∼0.05. Most importantly, detailed impedance data analyses of IN-T demonstrated that electron-pinned defect-dipoles, interfacial polarization and polaron hopping polarization contribute to the colossal permittivity at high temperatures (270 K); however, only the complexes (pinned electron) and polaron hopping polarization are active at low temperatures (below 180 K), which is consistent with UDR analysis.

A Complex Permittivity Based Sensor for the Electrical Characterization of High-Voltage Transformer Oils

PubMed Central

Dervos, Constantine T.; Paraskevas, Christos D.; Skafidas, Panayotis D.; Vassiliou, Panayota

2005-01-01

This work investigates the use of a specially designed cylindrical metal cell, in order to obtain complex permittivity and tanδ data of highly insulating High Voltage (HV) transformer oil samples. The data are obtained at a wide range of frequencies and operation temperatures to demonstrate the polarization phenomena and the thermally stimulated effects. Such complex permittivity measurements may be utilized as a criterion for the service life prediction of oil field electrical equipment (OFEE). Therefore, by one set of measurements on a small oil volume, data may be provided on the impending termination, or continuation of the transformer oil service life. The oil incorporating cell, attached to the appropriate measuring units, could be described as a complex permittivity sensor. In this work, the acquired dielectric data from a great number of operating distribution network power transformers were correlated to corresponding physicochemical ones to demonstrate the future potential employment of the proposed measuring technique.

Numerical investigation of nematic liquid crystals in the THz band based on EIT sensor.

PubMed

Wang, Peng-Yuan; Jin, Tao; Meng, Fan-Yi; Lyu, Yue-Long; Erni, Daniel; Wu, Qun; Zhu, Lei

2018-04-30

This paper introduces the concept of electromagnetically induced transparency (EIT) into the permittivity extraction of an anisotropic material-nematic liquid crystal (NLC). A novel two-step strategy is presented to extract the complex permittivity of the NLC at the THz band, which evaluates the relative permittivity tensor from the resonant frequencies and then determines the loss tangent from the quality factor Q of the EIT sensor. The proposed method features high accuracy due to the sharp resonance of the EIT sensor and also high robustness to the thickness of the NLC layer because only amplitude rather than phase information of the transmission coefficients is required. The NLC filled EIT sensor shows a sensitivity of 56.8 μm/RIU (the resonance wavelength shift over the refractive index change unit (RIU)) and Figure of Merit (FoM) of 6.92. The uncertainty of the proposed technique in the relative permittivity and loss tangent is 3% and 8.2%, respectively.

Polarimetric Signatures of Sea Ice. Part 1; Theoretical Model

NASA Technical Reports Server (NTRS)

Nghiem, S. V.; Kwok, R.; Yueh, S. H.; Drinkwater, M. R.

1995-01-01

Physical, structural, and electromagnetic properties and interrelating processes in sea ice are used to develop a composite model for polarimetric backscattering signatures of sea ice. Physical properties of sea ice constituents such as ice, brine, air, and salt are presented in terms of their effects on electromagnetic wave interactions. Sea ice structure and geometry of scatterers are related to wave propagation, attenuation, and scattering. Temperature and salinity, which are determining factors for the thermodynamic phase distribution in sea ice, are consistently used to derive both effective permittivities and polarimetric scattering coefficients. Polarimetric signatures of sea ice depend on crystal sizes and brine volumes, which are affected by ice growth rates. Desalination by brine expulsion, drainage, or other mechanisms modifies wave penetration and scattering. Sea ice signatures are further complicated by surface conditions such as rough interfaces, hummocks, snow cover, brine skim, or slush layer. Based on the same set of geophysical parameters characterizing sea ice, a composite model is developed to calculate effective permittivities and backscattering covariance matrices at microwave frequencies for interpretation of sea ice polarimetric signatures.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carvalho, N. C., E-mail: natalia.docarmocarvalho@research.uwa.edu.au; Le Floch, J-M.; Tobar, M. E.

The Y{sub 2}SiO{sub 5} (YSO) crystal is a dielectric material with biaxial anisotropy with known values of refractive index at optical frequencies. It is a well-known rare-earth (RE) host material for optical research and more recently has shown promising performance for quantum-engineered devices. In this paper, we report the first microwave characterization of the real permittivity tensor of a bulk YSO sample, as well as an investigation of the temperature dependence of the tensor components from 296 K down to 6 K. Estimated uncertainties were below 0.26%, limited by the precision of machining the cylindrical dielectric. Also, the electrical Q-factors of amore » few electromagnetic modes were recorded as a way to provide some information about the crystal losses over the temperature range. To solve the tensor components necessary for a biaxial crystal, we developed the multi-mode technique, which uses simultaneous measurement of low order whispering gallery modes. Knowledge of the permittivity tensor offers important data, essential for the design of technologies involving YSO, such as microwave coupling to electron and hyperfine transitions in RE doped samples at low temperatures.« less

CaCu3Ti4O12 particles and MWCNT-filled microwave absorber with improved microwave absorption by FSS incorporation

NASA Astrophysics Data System (ADS)

Qing, Yuchang; Yang, Zhaoning; Wen, Qinlong; Luo, Fa

2016-07-01

Multi-walled carbon nanotube (MWCNTs)- and CaCu3Ti4O12 (CCTO) particle-filled epoxy microwave absorbing coatings were prepared, and their electromagnetic properties and reflection loss (RL) were investigated in the frequency range 8.2-12.4 GHz. The microstructures of these coatings exhibit a uniform dispersion of MWCNTs and CCTO particles in the matrix. The value and frequency dependency of complex permittivity of such coatings enhanced with increasing MWCNT content. Frequency-selective surface was used to improve their microwave absorption (both the operating bandwidth and minimum RL) without increasing the absorber thickness. Such absorber showed high microwave absorbing performance, and the bandwidth of the RL below -8 dB (more than 84.1 % absorption) can be obtained in the whole X-band with a thickness of 1.5 mm.

Dielectric Spectroscopy of Biomolecules up to 110 GHz

NASA Astrophysics Data System (ADS)

Laux, Eva-Maria; Ermilova, Elena; Pannwitz, Daniel; Gibbons, Jessica; Hölzel, Ralph; Bier, Frank F.

2018-03-01

Radio-frequency fields in the GHz range are increasingly applied in biotechnology and medicine. In order to fully exploit both their potential and their risks detailed information about the dielectric properties of biological material is needed. For this purpose a measuring system is presented that allows the acquisition of complex dielectric spectra over 4 frequency decade up to 110 GHz. Routines for calibration and for data evaluation according to physicochemical interaction models have been developed. The frequency dependent permittivity and dielectric loss of some proteins and nucleic acids, the main classes of biomolecules, and of their sub-units have been determined. Dielectric spectra are presented for the amino acid alanine, the proteins lysozyme and haemoglobin, the nucleotides AMP and ATP, and for the plasmid pET-21, which has been produced by bacterial culture. Characterisation of a variety of biomolecules is envisaged, as is the application to studies on protein structure and function.

Synergistic method for boreal soil moisture and soil freeze retrievals using active and passive microwave instruments

NASA Astrophysics Data System (ADS)

Smolander, Tuomo; Lemmetyinen, Juha; Rautiainen, Kimmo; Schwank, Mike; Pulliainen, Jouni

2017-04-01

Soil moisture and soil freezing are important for diverse hydrological, biogeochemical, and climatological applications. They affect surface energy balance, surface and subsurface water flow, and exchange rates of carbon with the atmosphere. Soil freezing controls important biogeochemical processes, like photosynthetic activity of plants and microbial activity within soils. Permafrost covers approximately 24% of the land surface in the Northern Hemisphere and seasonal freezing occurs on approximately 51% of the area. The retrieval method presented is based on an inversion technique and applies a semiempirical backscattering model that describes the dependence of radar backscattering of forest as a function of stem volume, soil permittivity, the extinction coefficient of forest canopy, surface roughness, incidence angle, and radar frequency. It gives an estimate of soil permittivity using active microwave measurements. Applying a Bayesian assimilation scheme, it is also possible to use other soil permittivity retrievals to regulate this estimate to combine for example low resolution passive observations with high resolution active observations for a synergistic retrieval. This way the higher variance in the active retrieval can be constricted with the passive retrieval when at the same time the spatial resolution of the product is improved compared to the passive-only retrieval. The retrieved soil permittivity estimate can be used to detect soil freeze/thaw state by considering the soil to be frozen when the estimate is below a threshold value. The permittivity retrieval can also be used to estimate the relative moisture of the soil. The method was tested using SAR (Synthetic Aperture Radar) measurements from ENVISAT ASAR instrument for the years 2010-2012 and from Sentinel-1 satellite for the years 2015-2016 in Sodankylä area in Northern Finland. The synergistic method was tested combining the SAR measurements with a SMOS (Soil Moisture Ocean Salinity) radiometer based retrieval. The results were validated using in situ measurements from automatic soil state observation stations in Sodankylä calibration and validation (CAL-VAL) site, which is a reference site for several EO (Earth Observation) data products.

Characteristics of dielectric properties and conduction mechanism of TlInS2:Cu single crystals

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Ali, H. A. M.; El-Zaidia, E. F. M.

2013-12-01

Single crystals of TlInS2:Cu were grown by the modified Bridgman method. The dielectric behavior of TlInS2:Cu was investigated using the impedance spectroscopy technique. The real (ε1), imaginary (ε2) parts of complex dielectric permittivity and ac conductivity were measured in the frequency range (42-2×105) Hz with a variation of temperature in the range from 291 K to 483 K. The impedance data were presented in Nyquist diagrams for different temperatures. The frequency dependence of σtot (ω) follows the Jonscher's universal dynamic law with the relation σtot (ω)=σdc+Aωs, (where s is the frequency exponent). The mechanism of the ac charge transport across the layers of TlInS2:Cu single crystals was referred to the hopping over localized states near the Fermi level. The examined system exhibits temperature dependence of σac (ω), which showed a linear increase with the increase in temperature at different frequencies. Some parameters were calculated as: the density of localized states near the Fermi level, NF, the average time of charge carrier hopping between localized states, τ, and the average hopping distance, R.

The study of dielectric relaxation in aqueous carbohydrates solutions using time domain reflectometry technique

NASA Astrophysics Data System (ADS)

Hudge, Pravin G.; Lokhande, Milind P.; Kumbharkhane, Ashok C.

2012-09-01

Complex permittivity spectra of aqueous solutions of monosaccharide ( d-glucose) and disaccharides ( d-sucrose) in the frequency range from 10 MHz to 30 GHz at various concentrations and temperatures have been determined using time domain reflectometry technique. The complex dielectric permittivity spectrum of d-glucose and d-sucrose in water shows Cole-Davidson type behaviour. Dielectric constant (ɛ0) and relaxation time (τ), Kirkwood correlation factor, activation enthalpy and entropy parameters have been determined.

Dielectric properties of transformer paper impregnated by mineral oil based magnetic fluid

NASA Astrophysics Data System (ADS)

Timko, M.; Kopčanský, P.; Marton, K.; Tomčo, L.; Koneracká, M.

2010-01-01

The influence of combined magnetic and electric field on permittivity of transformer paper used in power transformers was observed. Transformer paper was impregnated by pure transformer oil ITO 100 and magnetic fluids based on transformer oil ITO 100 with different concentrations of magnetite nanoparticles. The measurements were carried out with help of high precision capacitance bridge. The electric intensity between circular planar electrodes was in the region of weak electric field (E > 106 V/m). The increase of electric permittivity of transformer paper impregnated by magnetic fluid opposite pure transformer paper was observed. The experiments showed that permittivity of insulator system consisting of pure transformer paper and impregnated transformer paper naturally depends on number of paper layers. The magnetodielectric effect was found to be dependent on magnetite nanoparticles concentration in magnetic fluids.

Electrostatic analysis of n-doped SrTiO{sub 3} metal-insulator-semiconductor systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamerbeek, A. M., E-mail: a.m.kamerbeek@rug.nl; Banerjee, T.; Hueting, R. J. E.

2015-12-14

Electron doped SrTiO{sub 3}, a complex-oxide semiconductor, possesses novel electronic properties due to its strong temperature and electric-field dependent permittivity. Due to the high permittivity, metal/n-SrTiO{sub 3} systems show reasonably strong rectification even when SrTiO{sub 3} is degenerately doped. Our experiments show that the insertion of a sub nanometer layer of AlO{sub x} in between the metal and n-SrTiO{sub 3} interface leads to a dramatic reduction of the Schottky barrier height (from around 0.90 V to 0.25 V). This reduces the interface resistivity by 4 orders of magnitude. The derived electrostatic analysis of the metal-insulator-semiconductor (n-SrTiO{sub 3}) system is consistent with thismore » trend. When compared with a Si based MIS system, the change is much larger and mainly governed by the high permittivity of SrTiO{sub 3}. The non-linear permittivity of n-SrTiO{sub 3} leads to unconventional properties such as a temperature dependent surface potential non-existent for semiconductors with linear permittivity such as Si. This allows tuning of the interfacial band alignment, and consequently the Schottky barrier height, in a much more drastic way than in conventional semiconductors.« less

Triggering Incipient Ferroelectricity in Calcium Copper Titanate (CaCu3Ti4O12) ceramics through partial B-site substitution with Te4+ ion

NASA Astrophysics Data System (ADS)

Barman, Nabadyuti; Varma, K. B. R.

Double perovskite structured dielectric ceramic CaCu3Ti4- x TexO12 (CCTTO) (x = 0, 0.05, 0.1, 0.15, 0.2) was fabricated from the powder obtained by conventional solid state synthetic route. The room temperature XRD patterns for the x = 0, 0.05, 0.075 modified samples were confirmed to possess a single phase with cubic space group Im3by Rietveld refinement. But, the Rietveld refinement performed on XRD patterns recorded for the compositions corresponding to x = 0.1, 0.15, 0.2 shows the coexistence of the cubic phase (space group Im3; a = 7.4065Å) and tetragonal phase (space group I4/mcm; a = 7.369 Å and c = 6.967 Å). The dielectric properties of these ceramics were studied over a wide frequency (40Hz-2MHz) and temperature range (30-400K). The Te4+ doped samples (CCTTO) exhibited dielectric permittivity (?r) value of ~23-33X103 which is more than twice that of undoped CCTO (~11x103) at 1kHz. A decreasing trend in dielectric permittivity with increasing temperature, a signature of incipient ferroelectricity, was observed for all the samples. Barrett's formula was invoked to rationalize the dielectric permittivity variation as a function of temperature. The incipient ferroelectric behavior is correlated with soft phonon mode observed in temperature dependent Raman Spectroscopic studies. .

In Situ Polymerization and Characterization of Highly Conducting Polypyrrole Fish Scales for High-Frequency Applications

NASA Astrophysics Data System (ADS)

Velhal, Ninad B.; Patil, Narayan D.; Puri, Vijaya R.

2015-12-01

Polypyrrole (Ppy) thin films on alumina were synthesized by an in situ chemical oxidative polymerization method at 300 K with equal monomer-to-oxidant ratio. Fourier transform infrared spectroscopy (FTIR) and FT-Raman spectroscopy confirmed the formation of Ppy. A thickness-dependent change from cauliflower to fish-scale morphology was observed. Microwave properties such as transmission, reflection, shielding effectiveness, permittivity, and microwave conductivity are reported in the frequency range from 8 GHz to 12 GHz. The direct-current (DC) conductivity varied from 9.45 × 10-3 S/cm to 17.29 × 10-3 S/cm, whereas the microwave conductivity varied from 63.07 S/cm to 349.08 S/cm. The shielding effectiveness varied between 6.18 dB and 10.39 dB.

Dielectric characterization of TiO2, Al2O3 - Nanoparticle loaded epoxy resin

NASA Astrophysics Data System (ADS)

Thakor, S. G.; Rana, V. A.; Vankar, H. P.

2018-05-01

In present work, the dielectric properties of two different nanoparticle loaded Bisphenol A-epoxy resin were carried out at room temperature. Sample of the neat epoxy resin and nanoparticle loaded epoxy resin in the form of disc were prepared of different weight fraction (i.e 0.5 wt%,0.7 wt%,1 wt%,1.5 wt%,1.7 wt%,2 wt%). TiO2 and Al2O3 nanoparticles were taken as filler in the epoxy resin. Complex permittivity of the prepared samples was measured using Agilent E4980A precision LCR meter in frequency range of 103 Hz to 106 Hz. The dependency of dielectric behavior on type and concentration of nanoparticle in considered frequency range are discussed in detail.

Transformation of nonlinear behaviors: from bright- to dark-gap soliton in a one-dimensional photonic crystal containing a nonlinear indefinite metamaterial defect.

PubMed

Zhang, Wei; Chen, Yuanyuan; Hou, Peng; Shi, Jielong; Wang, Qi

2010-12-01

Nonlinear propagation characteristics are investigated theoretically in a one-dimensional photonic band-gap structure doped with a nonlinear indefinite metamaterial defect for five distinct frequency intervals. It is found from the electric field distribution that there exists the bright gap solitonlike when the nonlinear indefinite metamaterial defect is a cut-off medium, while the dark gap solitonlike can appear in the nonlinear never cut-off defect layer. It is also found that there exists corresponding bistable lateral shift the properties of which are strongly dependent on the permittivity and permeability of nonlinear indefinite metamaterials. Moreover, in contrast to the switch-down threshold value, the switch-up threshold value is more sensitive to the incident frequency.

Dual percolation behaviors of electrical and thermal conductivity in metal-ceramic composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, K.; Zhang, Z. D.; Qian, L.

2016-02-08

The thermal and electrical properties including the permittivity spectra in radio frequency region were investigated for copper/yttrium iron garnet (Cu/YIG) composites. Interestingly, the percolation behaviors in electrical and thermal conductivity were obtained due to the formation of copper particles' networks. Beyond the electrical percolation threshold, negative permittivity was observed and plasmon frequency was reduced by several orders of magnitude. With the increase in copper content, the thermal conductivity was gradually increased; meanwhile, the phonon scattering effect and thermal resistance get enhanced, so the rate of increase in thermal conductivity gradually slows down. Hopefully, Cu/YIG composites with tunable electrical and thermalmore » properties have great potentials for electromagnetic interference shielding and electromagnetic wave attenuation.« less

REGENERATION AND REACTIVATION OF CARBON ADSORBENTS BY RADIO FREQUENCY INDUCTION HEATING

EPA Science Inventory

1. Electrical Properties of Adsorbents: We measured the electric permittivity of four commercially available carbon adsorbents (supplied by Wesvaco Inc) over the radio frequency range (1 to 40 MHz). Westvaco is by far the largest volume supplier of activated carbon...

Reconfigurable all-dielectric metamaterial frequency selective surface based on high-permittivity ceramics

NASA Astrophysics Data System (ADS)

Li, Liyang; Wang, Jun; Wang, Jiafu; Ma, Hua; Du, Hongliang; Zhang, Jieqiu; Qu, Shaobo; Xu, Zhuo

2016-04-01

Based on effective medium theory and dielectric resonator theory, we propose the design of reconfigurable all-dielectric metamaterial frequency selective surfaces (FSSs) using high-permittivity ceramics. The FSS is composed of ceramic resonators with different band stop responses under front and side incidences. By mechanically tuning the orientation of the ceramic resonators, reconfigurable electromagnetic (EM) responses between two adjacent stopbands can be achieved. The two broad stopbands originate from the first two resonant modes of the ceramic resonators. As an example, a reconfigurable FSS composed of cross-shaped ceramic resonators is demonstrated. Both numerical and experimental results show that the FSS can switch between two consecutive stopbands in 3.55-4.60 GHz and 4.54-4.94 GHz. The design method can be readily extended to the design of FSSs in other frequencies for high-power applications.

The Interaction of Radio-Frequency Fields With Dielectric Materials at Macroscopic to Mesoscopic Scales

PubMed Central

Baker-Jarvis, James; Kim, Sung

2012-01-01

The goal of this paper is to overview radio-frequency (RF) electromagnetic interactions with solid and liquid materials from the macroscale to the nanoscale. The overview is geared toward the general researcher. Because this area of research is vast, this paper concentrates on currently active research areas in the megahertz (MHz) through gigahertz (GHz) frequencies, and concentrates on dielectric response. The paper studies interaction mechanisms both from phenomenological and fundamental viewpoints. Relaxation, resonance, interface phenomena, plasmons, the concepts of permittivity and permeability, and relaxation times are summarized. Topics of current research interest, such as negative-index behavior, noise, plasmonic behavior, RF heating, nanoscale materials, wave cloaking, polaritonic surface waves, biomaterials, and other topics are overviewed. Relaxation, resonance, and related relaxation times are overviewed. The wavelength and material length scales required to define permittivity in materials is discussed. PMID:26900513

Conductivity and dielectric behaviour of PEO-based solid nanocomposite polymer electrolytes

NASA Astrophysics Data System (ADS)

Ibrahim, Suriani; Mohd Yasin, Siti Mariah; Nee, Ng Meng; Ahmad, Roslina; Johan, Mohd Rafie

2012-03-01

In this research, thin films of poly(ethylene oxide) (PEO) blend with lithium hexafluorophosphate (LiPF) salt and ethylene carbonate (EC) as plasticiser and carbon nanotube (CNT) as filler, are prepared using solution casting method. The conductivity and dielectric response of the nanocomposite polymer electrolyte systems are studied within the broad frequency range of 5 Hz-5 MHz and within a temperature range of 298-373 K. The conductivity-temperature plots are observed to be of Arrhenius nature. The dielectric behaviour is analysed using the dielectric permittivity (ɛr and ɛi), loss tangent (tanδ) and electric modulus (Mi and Mr) of the samples. It is observed that the dielectric permittivity rises sharply towards low frequencies due to electrode polarisation effects. The maxima of the loss tangent (tanδ) shifts towards higher frequencies and the height of the peak increases with increasing temperature.

Dielectric relaxation in Li2SO4 in the intermedia-temperature regime

NASA Astrophysics Data System (ADS)

Diosa, J. E.; Vargas, R. A.; Fernández, M. E.; Albinsson, I.; Mellander, B.-E.

2005-08-01

The dielectric permittivity of polycrystalline Li2SO4 was measured from 5 Hz to 13 MHz and over the temperature range 235-460 °C. The corrected imaginary part of permittivity, , and its real part vs. frequency clearly show a new dielectric relaxation around fmax = 2 × 104 Hz at T = 256 °C, which shifts to higher frequencies (1 MHz) as the temperatures increases. The relaxation frequency (calculated from the peak position of ) vs. reciprocal T shows an activated relaxation process with activation energy Ea= 0.9 eV, which is very close to that derived from the dc conductivity, E (0.87 eV). We suggest that this dielectric relaxation could be due to the Li+ jump and SO₄^- reorientation that cause distortion and change of the local lattice polarizability inducing dipoles like LiSO₄^-.

Reconfigurable all-dielectric metamaterial frequency selective surface based on high-permittivity ceramics

PubMed Central

Li, Liyang; Wang, Jun; Wang, Jiafu; Ma, Hua; Du, Hongliang; Zhang, Jieqiu; Qu, Shaobo; Xu, Zhuo

2016-01-01

Based on effective medium theory and dielectric resonator theory, we propose the design of reconfigurable all-dielectric metamaterial frequency selective surfaces (FSSs) using high-permittivity ceramics. The FSS is composed of ceramic resonators with different band stop responses under front and side incidences. By mechanically tuning the orientation of the ceramic resonators, reconfigurable electromagnetic (EM) responses between two adjacent stopbands can be achieved. The two broad stopbands originate from the first two resonant modes of the ceramic resonators. As an example, a reconfigurable FSS composed of cross-shaped ceramic resonators is demonstrated. Both numerical and experimental results show that the FSS can switch between two consecutive stopbands in 3.55–4.60 GHz and 4.54–4.94 GHz. The design method can be readily extended to the design of FSSs in other frequencies for high-power applications. PMID:27052098

A multi-frequency radiometric measurement of soil moisture content over bare and vegetated fields

NASA Technical Reports Server (NTRS)

Wang, J. R.; Schmugge, T. J.; Mcmurtrey, J. E., III; Gould, W. I.; Glazar, W. S.; Fuchs, J. E. (Principal Investigator)

1981-01-01

A USDA Beltsville Agricultural Research Center site was used for an experiment in which soil moisture remote sensing over bare, grass, and alfalfa fields was conducted over a three-month period using 0.6 GHz, 1.4 GHz, and 10.6 GHz Dicke-type microwave radiometers mounted on mobile towers. Ground truth soil moisture content and ambient air and sil temperatures were obtained concurrently with the radiometric measurements. Biomass of the vegetation cover was sampled about once a week. Soil density for each of the three fields was measured several times during the course of the experiment. Results of the radiometric masurements confirm the frequency dependence of moisture sensing sensitivity reduction reported earlier. Observations over the bare, wet field show that the measured brightness temperature is lowest at 5.0 GHz and highest of 0.6 GHz frequency, a result contrary to expectation based on the estimated dielectric permittivity of soil water mixtures and current radiative transfer model in that frequency range.

Electrical conductivity and dielectric behavior in sodium zinc divanadates

NASA Astrophysics Data System (ADS)

Sallemi, F.; Louati, B.; Guidara, K.

2014-11-01

The Na2ZnV2O7 compound was obtained by the conventional solid-state reaction. The sample was characterized by X-ray powder diffraction, Raman and impedance spectroscopy. The ac electrical conductivity and dielectric properties have been investigated in the frequency and temperature range of 200 Hz-1 MHz and 513 K-729 K, respectively. The direct current conductivity process is thermally activated. The frequency dependence of the conductivity is interpreted using the power law. The close values of activation energies obtained from the analysis of hopping frequency and dc conductivity implies that the transport is due to Na+ cation displacement parallel to (0 0 1) plane located between ZnO4 and VO4 tetrahedra. The evolution of the complex permittivity as a function of angular frequency was investigated. Several important parameters such as charge carrier concentration, ionic mobility and diffusion coefficient were determined. Thermodynamic parameters such as the free energy of activation ∆F, the enthalpy ∆H, and the change in entropy ∆S have been calculated.

Measurement of the complex permittivity of dry rocks and minerals: application of polythene dilution method and Lichtenecker's mixture formulae

NASA Astrophysics Data System (ADS)

Zheng, Yongchun; Wang, Shijie; Feng, Junming; Ouyang, Ziyuan; Li, Xiongyao

2005-12-01

The complex permittivity of dry rocks and minerals varies over a very wide range, even within a sample there are variation at different temperatures and frequencies. Most rocks and minerals are inhomogeneous materials, therefore, most of the present methods of dielectric measurement designed for artificial homogeneous materials are not suitable for rocks and minerals. The resonant cavity perturbation (RCP) method is a reliable and simple technique to determine the complex permittivity of dielectric materials in the GHz range, and this method is also used extensively. However, the traditional RCP method is sensitive to the measurement of low dielectric constant (ɛ') and low loss factor (ɛ'' or tanδ) materials. The complex permittivity of most dry rocks and minerals exceeds the span vibration of the RCP method, and cannot be measured by the RCP method directly. This paper proposes a new method to measure the complex permittivity of dry rocks and minerals with the RCP method incorporated in the application of polythene (PE) dilution method and Lichtenecker's mixture formulae. Dry rocks and minerals were ground into fine powder. The powder of rocks and minerals was mixed with polythene powder in a definite volume per cent. The mixture was heated and pressed into a thin circular slice. The slice was processed into a small rectangular strip sample, the size of which was fitted to the demands of the RCP method. The complex permittivity of the strip was obtained by the RCP method. The relationship between the dielectric properties of the two-phase mixture and those of each phase in the mixture can be expressed by Lichtenecker's mixture formula. Thus the complex permittivity of dry rocks and minerals can be calculated from the complex permittivity of the mixture in case the complex permittivity of polythene is known. The presented method was verified by measurements of reference materials of various known complex permittivity and other reliable dielectric measurement methods. The results of the experiment showed that this new method is of high accuracy, small sample requirement, and convenient application. Moreover, the complex permittivity of rocks and minerals measured by this method is more reliable than the direct dielectric measurement of rocks or minerals without application of the polythene dilution method and Lichtenecker's mixture formulae.

Intrinsic and extrinsic relaxation of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics: Effect of sintering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, J. Y.; Zhao, X. T.; Li, S. T.

2010-11-15

The effect of sintering process on the electrical properties of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) ceramic dielectrics were investigated in this paper. It was found that grain size is affected by sintering and the nonlinear current-voltage (I-V) property will decrease with the increased sintering time. Also, the frequency and temperature dependences of dielectric permittivity and loss in the ranges of 10{sup -1}-10{sup 7} Hz and 130-270 K were studied. Two relaxation processes with activation energy of 0.51 eV and 0.10 eV, respectively, were found in the frequency dependence of tan {delta} and Cole-Cole planes, which can be interpreted in termsmore » of insulating grain boundaries and semiconducting grains. It was suggested that grain boundary Maxwell-Wagner relaxation and ionization of oxygen vacancy V{sub O}{sup ++}, proposed as extrinsic and intrinsic relaxations, are responsible for the dielectric behaviors of CCTO ceramics.« less

Equilibrium electrodeformation of a spheroidal vesicle in an ac electric field

NASA Astrophysics Data System (ADS)

Nganguia, H.; Young, Y.-N.

2013-11-01

In this work, we develop a theoretical model to explain the equilibrium spheroidal deformation of a giant unilamellar vesicle (GUV) under an alternating (ac) electric field. Suspended in a leaky dielectric fluid, the vesicle membrane is modeled as a thin capacitive spheroidal shell. The equilibrium vesicle shape results from the balance between mechanical forces from the viscous fluid, the restoring elastic membrane forces, and the externally imposed electric forces. Our spheroidal model predicts a deformation-dependent transmembrane potential, and is able to capture large deformation of a vesicle under an electric field. A detailed comparison against both experiments and small-deformation (quasispherical) theory showed that the spheroidal model gives better agreement with experiments in terms of the dependence on fluid conductivity ratio, permittivity ratio, vesicle size, electric field strength, and frequency. The spheroidal model also allows for an asymptotic analysis on the crossover frequency where the equilibrium vesicle shape crosses over between prolate and oblate shapes. Comparisons show that the spheroidal model gives better agreement with experimental observations.

Frequency-dependent dielectric contribution of flexoelectricity allowing control of state switching in helicoidal liquid crystals

NASA Astrophysics Data System (ADS)

Outram, B. I.; Elston, S. J.

2013-07-01

The contribution of flexoelectric polarization to the dielectric susceptibility in helicoidal liquid crystals is formulated for the static equilibrium case, and further in the case of a time-varying field. A dispersion of the dielectric permittivity due to the frequency response of flexoelectric switching is described. The special case of a negative dielectric-anisotropy nematic material is considered and experimentally shown to agree with the analytical theory. It is further demonstrated how relaxation of the flexoelectric contribution to the dielectric tensor in this special case can be exploited to switch between states in cholesteric liquid crystal structures by altering the applied time-dependent field amplitude, if Δɛ<0 and (e1-e3)2/(K1+K3)>-Δɛɛ0. Consequentially, a versatile mechanism for driving between states in liquid crystal systems has been demonstrated and its implications for technology are suggested, and include dual-mode, bistable, and transflective displays.

Accuracy enhancement of laser induced breakdown spectra using permittivity and size optimized plasma confinement rings.

PubMed

Li, An; Guo, Shuai; Wazir, Nasrullah; Chai, Ke; Liang, Liang; Zhang, Min; Hao, Yan; Nan, Pengfei; Liu, Ruibin

2017-10-30

The inevitable problems in laser induced breakdown spectroscopy are matrix effect and statistical fluctuation of the spectral signal, which can be partly avoided by utilizing a proper confined unit. The dependences of spectral signal enhancement on relative permittivity were studied by varying materials to confine the plasma, which include polytetrafluoroethylene(PTFE), nylon/dacron, silicagel, and nitrile-butadiene rubber (NBR) with the relative permittivity 2.2, ~3.3, 3.6, 8~13, 15~22. We found that higher relative permittivity rings induce stronger enhancement ability, which restricts the energy dissipation of plasma better and due to the reflected electromagnetic wave from the wall of different materials, the electromagnetic field of plasma can be well confined and makes the distribution of plasma more orderly. The spectral intensities of the characteristic lines Si I 243.5 nm and Si I 263.1 nm increased approximately 2 times with relative permittivity values from 2.2 to ~20. The size dependent enhancement of PTFE was further checked and the maximum gain was realized by using a confinement ring with a diameter size of 5 mm and a height of 3 mm (D5mmH3mm), and the rings with D2mmH1mm and D3mmH2mm also show higher enhancement factor. In view of peak shift, peak lost and accidental peaks in the obtained spectra were properly treated in data progressing; the spectral fluctuation decreased drastically for various materials with different relative permittivities as confined units, which means the core of plasma is stabilized, attributing to the confinement effect. Furthermore, the quantitative analysis in coal shows wonderful results-the prediction fitting coefficient R 2 reaches 0.98 for ash and 0.99 for both volatile and carbon.

Low loss factor Co{sub 2}Z ferrite composites with equivalent permittivity and permeability for ultra-high frequency applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, Zhijuan; Chang, Hong; Sokolov, Alexander S.

2014-08-11

Ferrite composites of nominal composition Ba{sub 3}Co{sub 2+x}Ir{sub x}Fe{sub 24−2x}O{sub 41} were studied in order to achieve low magnetic and dielectric losses and equivalent permittivity and permeability over a frequency range of 0.3–1 GHz. Crystallographic structure was characterized by X-ray diffraction, which revealed a Z-type phase accompanied by increasing amounts of Y-type phase as the iridium amount was increased. The measured microwave dielectric and magnetic properties showed that the loss tan δ{sub ε} and loss tan δ{sub μ} decreased by 80% and 90% at 0.8 GHz with the addition of iridium of x = 0.12 and 0.15, respectively. An effective medium approximation was adopted to analyzemore » the composite ferrites having mixed phase structures. Moreover, adding Bi{sub 2}O{sub 3} enabled equivalent values of real permittivity and real permeability over the studied frequency range. The resultant data give rise to low loss factors, i.e., tan δ{sub ε}/ε′ = 0.008 and tan δ{sub μ}/μ′ = 0.037 at 0.8 GHz, while characteristic impedance was the same as that of free space.« less

Heterogeneities of 67P nucleus seen by CONSERT in the vicinity of Abydos

NASA Astrophysics Data System (ADS)

Ciarletti, Valerie; Lasue, Jéremie; Hérique, Alain; Kofman, Wlodek; Levasseur-Regourd, Anny-Chantal; Lemmonier, Florentin; Guiffaut, Christophe; Plettemeier, Dirk

2016-04-01

Since their arrival at comet 67P in August 2014, a number of instruments onboard Rosetta's main spacecraft and Philae lander have been observing the surface of the nucleus and have revealed details of amazing structures. This information was complemented by information about the nucleus internal structure collected by the CONSERT (Comet Nucleus Sounding Experiment by Radiowave Transmission) experiment in order to constrain the nucleus formation and evolution. The CONSERT experiment is a bistatic radar with receivers and transmitters on-board both Rosetta's main spacecraft and Philae lander. The instrument makes use of electromagnetic waves at 90 MHz that propagated, during the First Science Sequence, between Philae and Rosetta through the small lobe of 67P over distances ranging from approximately 200 to 800 m depending on the spacecraft location. The data used here have been collected at depths that reach a maximum of about one hundred of meters nucleus in the vicinity of Abydos. The data collected by CONSERT provide an estimate of the permittivity mean value and information about its spatial variability inside the sounded volume. Thanks to the 10 MHz frequency bandwidth of the signal used by the instrument a spatial resolution around 10m is obtained inside the sounded volume of the nucleus. In this paper, we specifically focus on local variations in the nucleus subsurface permittivity. A number of electromagnetic simulations corresponding to the CONSERT operations have been performed for a variety of subsurface permittivity models. The effect of local vertical and horizontal large scale variations as well as smaller scale random fractal structure of the permittivity values around the landing site will be presented and discussed in comparison with CONSERT's experimental data collected in the same configurations. Possible interpretations of the results will be presented as well as potential consequences for the nucleus structure in connection with observations made available by other instruments.

Synthesis of amplitude-versus-offset variations in ground-penetrating radar data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeng, X.; McMechan, G.A.; Xu, T.

2000-02-01

To evaluate the importance of amplitude-versus-offset information in the interpretation of ground-penetrating radar (GPR) data, GPR reflections are synthesized as a function of antenna separation using a 2.5-D Finite-difference solution of Maxwell's equations. The conductivity, the complex dielectric permittivity,and the complex magnetic permeability are varied systematically in nine suites of horizontally layered models. The source used is a horizontal transverse-electric dipole situated at the air-earth interface. Cole-Cole relaxation mechanisms define the frequency dependence of the media. Reflection magnitudes and their variations with antenna separation differ substantially, depending on the contrast in electromagnetic properties that caused the reflection. The spectral charactermore » of the dielectric and magnetic relaxations produces only second-order variations in reflection coefficients compared with those associated with contrasts in permittivity, conductivity, and permeability, so they may not be separable even when they are detected. In typical earth materials, attenuation of propagating GPR waves is influenced most strongly by conductivity, followed by dielectric relaxation, followed by magnetic relaxation. A pervasive feature of the simulated responses is locally high amplitude associated with the critical incident angle at the air-earth interface in the antenna radiation pattern. Full wavefield simulations of two field data sets from a fluvial/eolian environment are able to reproduce the main amplitude behaviors observed in the data.« less

A General Strategy to Achieve Colossal Permittivity and Low Dielectric Loss Through Constructing Insulator/Semiconductor/Insulator Multilayer Structures

NASA Astrophysics Data System (ADS)

Liu, Kai; Sun, Yalong; Zheng, Fengang; Tse, Mei-Yan; Sun, Qingbo; Liu, Yun; Hao, Jianhua

2018-06-01

In this work, we propose a route to realize high-performance colossal permittivity (CP) by creating multilayer structures of insulator/semiconductor/insulator. To prove the new concept, we made heavily reduced rutile TiO2 via annealing route in Ar/H2 atmosphere. Dielectric studies show that the maximum dielectric permittivity ( 3.0 × 104) of our prepared samples is about 100 times higher than that ( 300) of conventional TiO2. The minimum dielectric loss is 0.03 (at 104-105 Hz). Furthermore, CP is almost independent of the frequency (100-106 Hz) and the temperature (20-350 K). We suggest that the colossal permittivity is attributed to the high carrier concentration of the inner TiO2 semiconductor, while the low dielectric loss is due to the presentation of the insulator layer on the surface of TiO2. The method proposed here can be expanded to other material systems, such as semiconductor Si sandwiched by top and bottom insulator layers of Ga2O3.

Influence of the electromagnetic parameters on the surface wave attenuation in thin absorbing layers

NASA Astrophysics Data System (ADS)

Li, Yinrui; Li, Dongmeng; Wang, Xian; Nie, Yan; Gong, Rongzhou

2018-05-01

This paper describes the relationships between the surface wave attenuation properties and the electromagnetic parameters of radar absorbing materials (RAMs). In order to conveniently obtain the attenuation constant of TM surface waves over a wide frequency range, the simplified dispersion equations in thin absorbing materials were firstly deduced. The validity of the proposed method was proved by comparing with the classical dispersion equations. Subsequently, the attenuation constants were calculated separately for the absorbing layers with hypothetical relative permittivity and permeability. It is found that the surface wave attenuation properties can be strongly tuned by the permeability of RAM. Meanwhile, the permittivity should be appropriate so as to maintain high cutoff frequency. The present work provides specific methods and designs to improve the attenuation performances of radar absorbing materials.

Development of novel wireless sensor for food quality detection

NASA Astrophysics Data System (ADS)

Son Nguyen, Dat; Ngan Le, Nguyen; Phat Lam, Tan; Fribourg-Blanc, Eric; Chien Dang, Mau; Tedjini, Smail

2015-12-01

In this paper we present a wireless sensor for the monitoring of food quality. We integrate sensing capability into ultrahigh frequency (UHF) radio-frequency identification (RFID) tags through the relationship between the physical read-range and permittivity of the object we label with the RFID tags. Using the known variations of food permittivity as a function of time, we can detect the contamination time at which a food product becomes unacceptable for consumption based on the measurement of read-range with the as-designed sensing tags. This low-cost UHF RFID passive sensor was designed and experimentally tested on beef, pork, and cheese with the same storage conditions as in supermarkets. The agreement between the experimental and simulation results show the potential of this technique for practical application in food-quality tracking.

Dielectric properties of benzylamine in 1,2,6-hexanetriol mixture using time domain reflectometry technique

NASA Astrophysics Data System (ADS)

Swami, M. B.; Hudge, P. G.; Pawar, V. P.

The dielectric properties of binary mixtures of benzylamine-1,2,6-hexantriol mixtures at different volume fractions of 1,2,6-hexanetriol have been measured using Time Domain Reflectometry (TDR) technique in the frequency range of 10 MHz to 30 GHz. Complex permittivity spectra were fitted using Havriliak-Negami equation. By using least square fit method the dielectric parameters such as static dielectric constant (ɛ0), dielectric constant at high frequency (ɛ∞), relaxation time τ (ps) and relaxation distribution parameter (β) were extracted from complex permittivity spectra at 25∘C. The intramolecular interaction of different molecules has been discussed using the Kirkwood correlation factor, Bruggeman factor. The Kirkwood correlation factor (gf) and effective Kirkwood correlation factor (geff) indicate the dipole ordering of the binary mixtures.

Dielectric inspection of erythrocyte morphology.

PubMed

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

2008-05-21

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

Measurement of complex permittivities of biological materials and human skin in vivo in the frequency band

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghodgaonkar, D.K.

1987-01-01

A new method, namely, modified infinite sample method, has been developed which is particularly suitable for millimeter-wave dielectric measurements of biological materials. In this method, an impedance transformer is used which reduces the reflectivity of the biological sample. Because of the effect of introducing impendance transformer, the measured reflection coefficients are more sensitive to the complex permittivities of biological samples. For accurate measurement of reflection coefficients, two automated measurment systems were developed which cover the frequencies range of 26.5-60 GHz. An uncertainty analysis was performed to get an estimate of the errors in the measured complex permittivities. The dielectric propertiesmore » were measured for 10% saline solution, whole human blood, 200 mg/ml bovine serum albumin (BSA) solution and suspension of Saccharomyces cerevisiae cells. The Maxwell-Fricke equation, which is derived from dielectric mixture theory, was used for determination bound water in BSA solution. The results of all biological samples were interpreted by fitting Debye relaxation and Cole-Cole model. It is observed that the dielectric data for the biological materials can be explained on the basis of Debye relaxation of water molecule.« less

Negative index of refraction in metallic metamaterial comprising split-ring resonators.

PubMed

Dong, Zheng-Gao; Lei, Shuang-Ying; Xu, Ming-Xiang; Liu, Hui; Li, Tao; Wang, Fu-Ming; Zhu, Shi-Ning

2008-05-01

We numerically investigate the negative index of refraction in a metamaterial composed of metallic split-ring resonators, which exhibits simultaneously negative permittivity and permeability without resorting to additional metallic wires. It is confirmed that, in the left-handed band, negative permittivity is generated in analogy to the cut-wire metamaterial and negative permeability comes from the antisymmetric resonant mode, which occurs at a frequency band about 3 times higher than the fundamental magnetic resonance proposed by Pendry [IEEE Trans. Microwave Theory Tech. 47, 2075 (1999)].

Effect of optical damage resistant dopants on the dielectric properties of LiNbO3: Insight from broadband impedance spectroscopy and Raman scattering

NASA Astrophysics Data System (ADS)

Cochard, Charlotte; Guennou, Mael; Spielmann, Thiemo; van Hoof, Niels; Halpin, Alexei; Granzow, Torsten

2018-04-01

Optical damage limits the application range of congruent LiNbO3. This problem is commonly overcome by adding optical-damage-resistant cations. Here, the influence of doping with optical-damage-resistant Mg and Zn on the ionic and piezoelectric contributions to the dielectric permittivity is investigated in a broad frequency range (1 mHz-2 THz). It is shown that the two dopants have radically different influences on the variation of ionic permittivity with doping, in spite of their similarities with respect to the crystallographic structure. Raman spectroscopy reveals that the difference in permittivity can be traced to the effect of Mg and Zn doping on the susceptibility of the phonon modes. Both observations point to differences in the defect incorporation mechanisms.

Temporal solitons in magnetooptic and metamaterial waveguides

NASA Astrophysics Data System (ADS)

Boardman, A. D.; Hess, O.; Mitchell-Thomas, R. C.; Rapoport, Y. G.; Velasco, L.

2010-09-01

The important topic of temporal soliton propagation in double-negative metamaterials is discussed with an emphasis upon short pulses that exhibit self-steepening controlled by the frequency dependence of the relative permittivity and permeability. In addition, magnetooptic control is included, leading to some fascinating outcomes that should have practical application. The role of self-steepening, Raman scattering, third-order dispersion and magnetooptics is thoroughly investigated, and it is shown that pulses can acquire signatures in the form of additional velocities with respect to the moving frame. The metamaterial influence upon self-steepening has such a strong frequency dependence that it can be used to combat Raman scattering. The self-steepening can change sign, and it is shown that it is possible to arrange pulses in special switching formats to organise the output times. The metamaterial influence upon bit-patterns admits an important degree of control over multi-pulse interactions, and this is combined with magnetooptics to restore patterns. The role of third-order dispersion is also presented. Again, a control of the pulse behaviour in the neighbourhood where the frequency dependence causes the group-velocity dispersion parameter to approach zero is a direct consequence of using this kind of metamaterial. Finally, a Lagrangian analysis is used to support simulations of the positions of the pulse maxima.

Origin of colossal dielectric permittivity of rutile Ti 0.9In 0.05Nb 0.05O 2: single crystal and polycrystalline

DOE PAGES

Song, Yongli; Wang, Xianjie; Sui, Yu; ...

2016-02-12

Here in this article, we investigated the dielectric properties of (In + Nb) co-doped rutile TiO 2 single crystal and polycrystalline ceramics. Both of them showed colossal, up to 10 4, dielectric permittivity at room temperature. The single crystal sample showed one dielectric relaxation process with a large dielectric loss. The voltage-dependence of dielectric permittivity and the impedance spectrum suggest that the high dielectric permittivity of single crystal originated from the surface barrier layer capacitor (SBLC). The impedance spectroscopy at different temperature confirmed that the (In+Nb) co-doped rutile TiO 2 polycrystalline ceramic had semiconductor grains and insulating grain boundaries, andmore » that the activation energies were calculated to be 0.052 eV and 0.35 eV for grain and grain boundary, respectively. The dielectric behavior and impedance spectrum of the polycrystalline ceramic sample indicated that the internal barrier layer capacitor (IBLC) mode made a major contribution to the high ceramic dielectric permittivity, instead of the electron-pinned defect-dipoles.« less

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

PubMed Central

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

2016-01-01

In this paper, we investigated the dielectric properties of (In + Nb) co-doped rutile TiO2 single crystal and polycrystalline ceramics. Both of them showed colossal, up to 104, dielectric permittivity at room temperature. The single crystal sample showed one dielectric relaxation process with a large dielectric loss. The voltage-dependence of dielectric permittivity and the impedance spectrum suggest that the high dielectric permittivity of single crystal originated from the surface barrier layer capacitor (SBLC). The impedance spectroscopy at different temperature confirmed that the (In + Nb) co-doped rutile TiO2 polycrystalline ceramic had semiconductor grains and insulating grain boundaries, and that the activation energies were calculated to be 0.052 eV and 0.35 eV for grain and grain boundary, respectively. The dielectric behavior and impedance spectrum of the polycrystalline ceramic sample indicated that the internal barrier layer capacitor (IBLC) mode made a major contribution to the high ceramic dielectric permittivity, instead of the electron-pinned defect-dipoles. PMID:26869187

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

NASA Astrophysics Data System (ADS)

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

2016-02-01

In this paper, we investigated the dielectric properties of (In + Nb) co-doped rutile TiO2 single crystal and polycrystalline ceramics. Both of them showed colossal, up to 104, dielectric permittivity at room temperature. The single crystal sample showed one dielectric relaxation process with a large dielectric loss. The voltage-dependence of dielectric permittivity and the impedance spectrum suggest that the high dielectric permittivity of single crystal originated from the surface barrier layer capacitor (SBLC). The impedance spectroscopy at different temperature confirmed that the (In + Nb) co-doped rutile TiO2 polycrystalline ceramic had semiconductor grains and insulating grain boundaries, and that the activation energies were calculated to be 0.052 eV and 0.35 eV for grain and grain boundary, respectively. The dielectric behavior and impedance spectrum of the polycrystalline ceramic sample indicated that the internal barrier layer capacitor (IBLC) mode made a major contribution to the high ceramic dielectric permittivity, instead of the electron-pinned defect-dipoles.

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

PubMed

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

2016-02-12

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

Molecular dynamics simulations of the dielectric properties of fructose aqueous solutions

NASA Astrophysics Data System (ADS)

Sonoda, Milton T.; Elola, M. Dolores; Skaf, Munir S.

2016-10-01

The static dielectric permittivity and dielectric relaxation properties of fructose aqueous solutions of different concentrations ranging from 1.0 to 4.0 mol l-1 are investigated by means of molecular dynamics simulations. The contributions from intra- and interspecies molecular correlations were computed individually for both the static and frequency-dependent dielectric properties, and the results were compared with the available experimental data. Simulation results in the time- and frequency-domains were analyzed and indicate that the presence of fructose has little effect on the position of the fast, high-frequency (>500 cm-1) components of the dielectric response spectrum. The low-frequency (<0.1 cm-1) components, however, are markedly influenced by sugar concentration. Our analysis indicates that fructose-fructose and fructose-water interactions strongly affect the rotational-diffusion regime of molecular motions in the solutions. Increasing fructose concentration not only enhances sugar-sugar and sugar-water low frequency contributions to the dielectric loss spectrum but also slows down the reorientational dynamics of water molecules. These results are consistent with previous computer simulations carried out for other disaccharide aqueous solutions.

Ground EMI: designing the future trends in shallow depth surveying

NASA Astrophysics Data System (ADS)

Thiesson, J.; Schamper, C.; Simon, F. X.; Tabbagh, A.

2017-12-01

In theory, electromagnetic induction phenomena are driven by three fundamental properties (conductivity, susceptibility, permittivity). Since the 1930's, the developments of EMI prospecting were based on assumptions (Low frequency VS High frequency, low/high induction number). The design of the devices was focused on specific aims (diffusive/propagative, mapping/sounding) and, in the last thirty years the progressive transition from analog to numeric electronics completely enhanced the potency of measurements (multi-channeling, automatic positioning) a) as it did in model computation. In the field of metric sized devices for lower depths of investigation, the measurements have been first restricted to electrical conductivity. However, the measurement of the magnetic susceptibility proved to be possible thanks to in phase and quadrature separation, and the last developed commercially available multi-frequency and/or multi-receivers devices permit, thanks to accurate calibration, the measurements of the three properties with various geometries or frequencies simultaneously. The aims of this study is to present theoretical results in order to give hints for designing a device which can be optimal to evaluate the three properties and their frequency dependence.

Dielectric Relaxation of CaCu3Ti4O12 synthesized from a pyrolysis method

NASA Astrophysics Data System (ADS)

Liu, Jianjun; Mei, W. N.; Smith, R. W.; Hardy, J. R.

2006-03-01

Giant dielectric constant material CaCu3Ti4O12 has been synthesized by using a pyrolysis method. A stable solution was made by dissolving calcium nitrate, copper nitrate, and titanium isopropoxide in 2-methoxyethanol; the solution was then heated at 500 and 700 ^oC for 2 hours to obtain a pure phase of CaCu3Ti4O12. The frequency and temperature dependences of dielectric permittivity were examined in the ranges of 10-1˜10^6 Hz and -150˜200 ^oC. We found that the dielectric properties of the sample were the same as those made from solid state reaction. Specifically, there is a Debye-like relaxation at low temperature and its giant dielectric constant about 11000 is independent of the temperature and frequency over a wide range.

Characterization of transceive surface element designs for 7 tesla magnetic resonance imaging of the prostate: radiative antenna and microstrip.

PubMed

Ipek, O; Raaijmakers, A J E; Klomp, D W J; Lagendijk, J J W; Luijten, P R; van den Berg, C A T

2012-01-21

Ultra-high field magnetic resonance (≥7 tesla) imaging (MRI) faces challenges with respect to efficient spin excitation and signal reception from deeply situated organs. Traditional radio frequency surface coil designs relying on near-field coupling are suboptimal at high field strengths. Better signal penetration can be obtained by designing a radiative antenna in which the energy flux is directed to the target location. In this paper, two different radiative antenna designs are investigated to be used as transceive elements, which employ different dielectric permittivities for the antenna substrate. Their transmit and receive performances in terms of B(+)(1), local SAR (specific absorption rate) and SNR (signal-to-noise ratio) were compared using extensive electromagnetic simulations and MRI measurements with traditional surface microstrip coils. Both simulations and measurements demonstrated that the radiative element shows twofold gain in B(+)(1) and SNR at 10 cm depth, and additionally a comparable SAR peak value. In terms of transmit performance, the radiative antenna with a dielectric permittivity of 37 showed a 24% more favorable local SAR(10g avg)/(B(+)(1))(2) ratio than the radiative antenna with a dielectric permittivity of 90. In receive, the radiative element with a dielectric permittivity of 90 resulted in a 20% higher SNR for shallow depths, but for larger depths this difference diminished compared to the radiative element with a dielectric permittivity of 37. Therefore, to image deep anatomical regions effectively, the radiative antenna with a dielectric permittivity of 37 is favorable.

Temperature characterization of dielectric permittivity and AC conductivity of nano copper oxide-doped polyaniline composite

NASA Astrophysics Data System (ADS)

Shubha, L. N.; Madhusudana Rao, P.

2016-06-01

The polyaniline/copper oxide (PANI/CuO) nanocomposite was prepared by mixing solutions of polyaniline and copper oxide nanoparticles in dimethyl sulfoxide (DMSO). The synthesized polymer nanocomposites were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM) and UV-visible spectroscopy. The characteristic peaks in XRD and UV-visible spectra confirmed the presence of CuO in the polymer structure. SEM images indicated morphological changes in the composite matrix as compared to the pristine PANI. The DC conductivity measurements were performed using two-probe method for various temperatures. AC conductivity and dielectric response of the composites were investigated in the frequency range of 102-106Hz using LCR meter. Dielectric permittivity ɛ‧(w) and dielectric loss factor ɛ‧‧(w) were investigated. It was observed that ɛ‧(w) and ɛ‧‧(w) decrease with increase in frequency at all temperatures. At a particular frequency it is observed that both ɛ‧(w) and ɛ‧‧(w) increase with increase in temperature. It was also observed that AC conductivity increased with increase in frequency and temperature.

Relaxor-ferroelectric crossover in (B i1 /2K1 /2)Ti O3 : Origin of the spontaneous phase transition and the effect of an applied external field

NASA Astrophysics Data System (ADS)

Hagiwara, Manabu; Ehara, Yoshitaka; Novak, Nikola; Khansur, Neamul H.; Ayrikyan, Azatuhi; Webber, Kyle G.; Fujihara, Shinobu

2017-07-01

The temperature evolution of polar order in an A -site complex perovskite (B i1 /2K1 /2)Ti O3 (BKT) has been investigated by measurements of dielectric permittivity, depolarization current, and stress-stain curves at elevated temperatures. Upon cooling from high temperatures, BKT first enters a relaxor state and then spontaneously transforms into a ferroelectric state. The analyses of temperature and frequency dependence of permittivity have revealed that polar nanoregions of the relaxor phase appear at temperatures higher than 560°C, and also that their freezing at 296°C triggers the spontaneous relaxor-ferroelectric transition. We discuss the key factors determining the development of long-range polar order in A -site complex perovskites through a comparison with the relaxor (B i1 /2N a1 /2)Ti O3 . We also show that application of biasing electric fields and compressive stresses to BKT favors its ferroelectric phase, resulting in a significant shift of the relaxor-ferroelectric transition temperature towards higher temperatures. Based on the obtained results, electric field-temperature and stress-temperature phase diagrams are firstly determined for BKT.

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.

Structure and dielectric properties of Na0.5Bi0.5TiO3-CaTiO3 solid solutions

NASA Astrophysics Data System (ADS)

Birks, E.; Dunce, M.; Ignatans, R.; Kuzmin, A.; Plaude, A.; Antonova, M.; Kundzins, K.; Sternberg, A.

2016-02-01

Despite wide studies of Na0.5Bi0.5TiO3, structure of this material and its connection with the observed physical properties still raise numerous questions due to mutually contradicting results obtained. Here, structure and dielectric properties of poled and unpoled Na0.5Bi0.5TiO3-CaTiO3 solid solutions are studied, projecting the obtained concentration dependence of structure and dielectric properties on pure Na0.5Bi0.5TiO3 as the end member of this material group. X-ray diffraction patterns for Na0.5Bi0.5TiO3-CaTiO3 solid solutions reveal dominating of an orthorhombic Pnma phase, even for the compositions approaching the end composition (Na0.5Bi0.5TiO3), whereas structure of pure Na0.5Bi0.5TiO3 can be considered, assuming coexistence of rhombohedral and orthorhombic phases. This allows one to avoid appearance of a large difference of rhombohedral distortions between the unpoled and poled Na0.5Bi0.5TiO3, if the rhombohedral distortion is calculated as for single R3c phase. Features of dielectric permittivity, corresponding to the observed structural phase transition, are identified. It is discussed that the rhombohedral R3c phase is responsible for appearance of the frequency-dependent shoulder of dielectric permittivity temperature dependence, characteristic for unpoled Na0.5Bi0.5TiO3.

Measurement Of Multiphase Flow Water Fraction And Water-cut

NASA Astrophysics Data System (ADS)

Xie, Cheng-gang

2007-06-01

This paper describes a microwave transmission multiphase flow water-cut meter that measures the amplitude attenuation and phase shift across a pipe diameter at multiple frequencies using cavity-backed antennas. The multiphase flow mixture permittivity and conductivity are derived from a unified microwave transmission model for both water- and oil-continuous flows over a wide water-conductivity range; this is far beyond the capability of microwave-resonance-based sensors currently on the market. The water fraction and water cut are derived from a three-component gas-oil-water mixing model using the mixture permittivity or the mixture conductivity and an independently measured mixture density. Water salinity variations caused, for example, by changing formation water or formation/injection water breakthrough can be detected and corrected using an online water-conductivity tracking technique based on the interpretation of the mixture permittivity and conductivity, simultaneously measured by a single-modality microwave sensor.

Analytic description of microcylindrical cavity for surface plasmon polariton

NASA Astrophysics Data System (ADS)

Tekkozyan, Vahan; Babajanyan, Arsen; Nerkararyan, Khachatur

2013-09-01

We consider the formation of the surface plasmon polariton (SPP) mode in the microcylinder cavity. Developed theoretical model allows to analytically calculate the closed-form expressions for the mode field distributions, resonant frequency, as well as the radiation and dissipative parts of quality factor of the structure in a broad wavelength range. For the conditions when a radius of a metallic cylinder is in order of SPP's wavelength, the highest value of Q-factor is achieved in infrared region of the spectrum where the absolute value of the real part of dielectric permittivity of the metal is much more than both the imaginary part of dielectric permittivity of the metal and the dielectric permittivity of surrounding media. Also, the radiation losses decrease with increasing of radius of cylinder. The obtained results give opportunity to find optimal conditions for having efficient emission in microcylinder cavity and it can serve as practical guidelines to design SPP microcavity for stimulated emission.

Anomalous resonances of an optical microcavity with a hyperbolic metamaterial core

NASA Astrophysics Data System (ADS)

Travkin, Evgenij; Kiel, Thomas; Sadofev, Sergey; Busch, Kurt; Benson, Oliver; Kalusniak, Sascha

2018-05-01

We embed a hyperbolic metamaterial based on stacked layer pairs of epitaxially grown ZnO/ZnO:Ga in a monolithic optical microcavity, and we investigate the arising unique resonant effects experimentally and theoretically. Unlike traditional metals, the semiconductor-based approach allows us to utilize all three permittivity regions of the hyperbolic metamaterial in the near-infrared spectral range. This configuration gives rise to modes of identical orders appearing at different frequencies, a zeroth-order resonance in an all-positive permittivity region, and a continuum of high-order modes. In addition, an unusual lower cutoff frequency is introduced to the resonator mode spectrum. The observed effects expand the possibilities for customization of optical resonators; in particular, the zeroth-order and high-order modes hold strong potential for the realization of deeply subwavelength cavity sizes.

Accurate determination of dielectric permittivity of polymers from 75  GHz to 1.6  THz using both S-parameters and transmission spectroscopy.

PubMed

Chang, Tianying; Zhang, Xiansheng; Zhang, Xiaoxuan; Cui, Hong-Liang

2017-04-20

Interactions of terahertz (THz) electromagnetic radiation with polymer materials have been studied recently with increasing depth and breadth, for purposes of both using polymers in fabricating THz optical components such as lenses, waveplates, waveguides, and sample holders/containers, and employing THz spectral imaging as a new tool for nondestructive testing of polymer composite structures. Either endeavor cannot even begin without a quantitative knowledge of the complex dielectric permittivity, i.e., the propagation and attenuation properties of such polymers in the requisite wave band. In this paper, a number of non-polar and non-magnetic polymers, such as polytetrafluoroethylene, polypropylene, high-density polyethylene, and polymethyl methacrylate, are studied for the purpose of determining their complex dielectric permittivity, including its real part and imaginary parts, in the wide frequency band from millimeter wave to THz wave (75 GHz-1.6 THz), in two ways. The first is a free space method based on a vector network analyzer covering the frequency region from 75 to 500 GHz, and the second is the THz time-domain spectroscopy (THz-TDS), effective for the region of 100 GHz-1.6 THz. The results are consistent with existing data (with discrepancies less than 1% in most cases for both the index of refraction and the absorption coefficient), and where they overlap in frequency coverage, the two methods yield identical results to within measurement error.

Analysis of long wavelength electromagnetic scattering by a magnetized cold plasma prolate spheroid

NASA Astrophysics Data System (ADS)

Ahmadizadeh, Yadollah; Jazi, Bahram; Abdoli-Arani, Abbas

2013-08-01

Using dielectric permittivity tensor of the magnetized prolate plasma, the scattering of long wavelength electromagnetic waves from the mentioned object is studied. The resonance frequency and differential scattering cross section for the backward scattered waves are presented. Consistency between the resonance frequency in this configuration and results obtained for spherical plasma are investigated. Finally, the effective factors on obtained results such as incident wave polarization, the frequency of the incident wave, the plasma frequency and the cyclotron frequency are analyzed.

Evidence of Kittel type behaviour of the permittivity of a nanostructured high sensitivity piezoelectric

NASA Astrophysics Data System (ADS)

BalčiÅ«nas, Sergejus; Ivanov, Maksim; Grigalaitis, Robertas; Banys, Juras; Amorín, Harvey; Castro, Alicia; Algueró, Miguel

2018-05-01

The broadband dielectric properties of high sensitivity piezoelectric 0.36BiScO3-0.64PbTiO3 ceramics with average grain sizes from 1.6 μm down to 26 nm were investigated in the 100-500 K temperature range. The grain size dependence of the dielectric permittivity was analysed within the effective medium approximation. It was found that the generalised core-shell (or brick wall) model correctly explains the size dependence down to the nanoscale. For the first time, the grain bulk and boundary properties were obtained without making any assumptions of values of the parameters or simplifications. Two contributions to dielectric permittivity of the grain bulk are described. The first is the size-independent one, which follows the Curie-Weiss law. The second one is shown to plausibly follow the Kittel's law. This seems to suggest the unexpected persistence of mobile ferroelectric domains at the nanoscale (26 nm grains). Alternative explanations are discussed.

A transmission line method for the measurement of microwave permittivity and permeability

NASA Astrophysics Data System (ADS)

Lederer, P. G.

1990-12-01

A method for determining complex permittivity and permeability at microwave frequencies from two port S parameter measurements of lossy solids in coaxial or waveguide transmission lines is described. The use of the TRL (Through Reflect Line) calibration scheme allows the measuring system to be calibrated right up to the specimen faces thereby eliminating most of the sample cell from the measurement and allowing suitable materials to be molded directly into the specimen cell in order to eliminate air gaps between specimen and transmission line walls. Some illustrative measurements for dielectric and magnetic materials are presented.

Trends of microwave dielectric materials for antenna application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sulong, T. A. T., E-mail: tuanamirahtuansulong@gmail.com; Osman, R. A. M., E-mail: rozana@unimap.edu.my; Idris, M. S., E-mail: sobri@unimap.edu.my

Rapid development of a modern microwave communication system requires a high quality microwave dielectric ceramic material to be used as mobile and satellite communication. High permittivity of dielectric ceramics leads to fabrication of compact device for electronic components. Dielectric ceramics which used for microwave applications required three important parameters such as high or appropriate permittivity (ε{sub r}), high quality factor (Q {sub f} ≥ 5000 GH z) and good temperature coefficient of resonant frequency (τ{sub f}). This paper review of various dielectric ceramic materials used as microwave dielectric materials and related parameters for antenna applications.

Electric properties of nanostructure (FeCoZr)x(CaF2)(100-x) produced in argon Ar atmosphere

NASA Astrophysics Data System (ADS)

Bondariev, Vitalii; Czarnacka, Karolina; Boiko, Oleksandr

2015-09-01

The paper presents frequency f and temperature Tp dependences of conductivity σ, capacitance Cp and phase shift angle θ for the nanocomposite metal-dielectric (FeCoZr)x(CaF2)(100-x). Samples of nanocomposite were produced by ion-beam sputtering in pure argon Ar atmosphere. Partial pressure of gas Ar in the ion source pAr=1.1×10-1Pa. Contains of metallic phase in tested sample is x = 54.6 at.%. Studies carried out by stand to measuring of AC electrical properties of nanocomposites and semiconductors. The measurements have been performed using alternating current within the frequency range of 50 Hz - 1 MHz for measuring temperatures ranging from 77 K to 373 K. On the frequency-temperature dependence of phase shift angle θ at low frequencies phase shift have capacitive character and at high frequencies - inductive. Position of fmin on the frequency dependence on capacitance Cp corresponds exactly to the resonance frequency fR for which the angle θ crosses zero. Analysis of the results showed that phenomena similar to phenomena in conventional circuit RLC occur in the nanocomposite (CoFeZr)54.6(CaF2)45.4. Jumping recharging between the defects leads to the formation of dipoles and consequently to the increase of permittivity. After a time τ electron returns to the first defect and dipole disappears. The formation of inductance in nanocomposite is associated with return jumps of electrons from defect with negative charge to the defect with positive charge, set by the time, which are characterized by low values of activation energy.

Microwave and millimeter wave dielectric permittivity and magnetic permeability of epsilon-gallium-iron-oxide nano-powders

NASA Astrophysics Data System (ADS)

Chao, Liu; Afsar, Mohammed N.; Ohkoshi, Shin-ichi

2015-05-01

In millimeter wave frequency range, hexagonal ferrites with high uniaxial anisotropic magnetic fields are used as absorbers. These ferrites include M-type barium ferrite (BaFe12O19) and strontium ferrite (SrFe12O19), which have natural ferromagnetic resonant frequency range from 40 GHz to 60 GHz. However, the higher frequency range lacks suitable materials that support the higher frequency ferromagnetic resonance. A series of gallium-substituted ɛ-iron oxides (ɛ-GaxFe2-xO3) are synthesized, which have ferromagnetic resonant frequencies appearing over the frequency range of 30 GHz to 150 GHz. The ɛ-GaxFe2-xO3 is synthesized by the sol-gel method. The particle sizes are observed to be smaller than 100 nm. In this paper, in-waveguide transmission and reflection method and the free space magneto-optical approach have been employed to study these newly developed ɛ-GaxFe2-xO3 particles in millimeter waves. These techniques enable to obtain precise transmission spectra to determine the dielectric and magnetic properties of both isotropic and anisotropic ferrites in the microwave and millimeter wave frequency range from single set of direct measurements. The complex dielectric permittivity and magnetic permeability spectra of ɛ-GaxFe2-xO3 are shown in this paper. Strong ferromagnetic resonances at different frequencies determined by the x parameter are found.

Tissue dielectric measurement using an interstitial dipole antenna.

PubMed

Wang, Peng; Brace, Christopher L

2012-01-01

The purpose of this study was to develop a technique to measure the dielectric properties of biological tissues with an interstitial dipole antenna based upon previous efforts for open-ended coaxial probes. The primary motivation for this technique is to facilitate treatment monitoring during microwave tumor ablation by utilizing the heating antenna without additional intervention or interruption of the treatment. The complex permittivity of a tissue volume surrounding the antenna was calculated from reflection coefficients measured after high-temperature microwave heating by using a rational function model of the antenna's input admittance. Three referencing liquids were needed for measurement calibration. The dielectric measurement technique was validated ex vivo in normal and ablated bovine livers. Relative permittivity and effective conductivity were lower in the ablation zone when compared to normal tissue, consistent with previous results. The dipole technique demonstrated a mean 10% difference of permittivity values when compared to open-ended coaxial cable measurements in the frequency range of 0.5-20 GHz. Variability in measured permittivities could be smoothed by fitting to a Cole-Cole dispersion model. Further development of this technique may facilitate real-time monitoring of microwave ablation treatments through the treatment applicator. © 2011 IEEE

Tissue Dielectric Measurement Using an Interstitial Dipole Antenna

PubMed Central

Wang, Peng; Brace, Christopher L.

2012-01-01

The purpose of this study was to develop a technique to measure the dielectric properties of biological tissues with an interstitial dipole antenna based upon previous efforts for open-ended coaxial probes. The primary motivation for this technique is to facilitate treatment monitoring during microwave tumor ablation by utilizing the heating antenna without additional intervention or interruption of the treatment. The complex permittivity of a tissue volume surrounding the antenna was calculated from reflection coefficients measured after high-temperature microwave heating by using a rational function model of the antenna’s input admittance. Three referencing liquids were needed for measurement calibration. The dielectric measurement technique was validated ex vivo in normal and ablated bovine livers. Relative permittivity and effective conductivity were lower in the ablation zone when compared to normal tissue, consistent with previous results. The dipole technique demonstrated a mean 10% difference of permittivity values when compared to open-ended coaxial cable measurements in the frequency range of 0.5–20 GHz. Variability in measured permittivities could be smoothed by fitting to a Cole–Cole dispersion model. Further development of this technique may facilitate real-time monitoring of microwave ablation treatments through the treatment applicator. PMID:21914566

Structural and electrical characterisation of Li(2)O : TiO(2) : SnO(2) : P(2)O(5) electrolyte glass.

PubMed

Abrahams, Isaac; Hadzifejzovic, Emina; Dygas, Jozef R

2004-10-07

Glasses of general formula 50Li(2)O : xSnO(2) : (10 -x)TiO(2) : 40P(2)O(5)(0.0 < or = x < or = 10) were investigated by differential scanning calorimetry, X-ray diffraction and ac impedance, (31)P solid-state NMR and IR spectroscopies. Three isotropic resonances can be identified in the (31)P NMR spectra, which have been assigned to various phosphate species. Analysis of the ratios of integrated intensities in the (31)P spectra leads to models for the Ti and Sn coordination environments. Both TiO(2) and SnO(2) are found to be predominantly network forming with Ti and Sn proposed to be in five- and four-coordinate environments respectively. Analysis of ac impedance spectra collected at low temperatures reveals two forms of permittivity dispersion, viz: high frequency conductivity dispersion and Cole-Cole type relaxation of permittivity. The activation energy of the relaxation frequency of the permittivity dispersion is equal to that of the dc conductivity, which is consistent with cooperative motion of lithium ions. The results also suggest that the observed increase in conductivity with temperature appears to be mainly due to an increase in mobility rather than increase in carrier concentration.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mekni, Omar, E-mail: omarmekni-lmop@yahoo.fr; Arifa, Hakim; Askri, Besma

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 ε{sup ´} and the dissipation factor Tan(δ). We prove that themore » evolution of the imaginary part of the complex permittivity against temperature ε{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.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niknam, A. R., E-mail: a-niknam@sbu.ac.ir; Rastbood, E.; Khorashadizadeh, S. M.

The dielectric permittivity tensor of a magnetoactive current-driven plasma is obtained by employing the kinetic theory based on the Vlasov equation and Lorentz transformation formulas with an emphasize on the q-nonextensive statistics. By deriving the q-generalized dispersion relation of the low frequency modes in this plasma system, the possibility and properties of filamentation and ion acoustic instabilities are then studied. It is shown that the occurrence and the growth rate of these instabilities depend strongly on the nonextensive parameters, external magnetic field strength, and drift velocity. It is observed that the growth rate of ion acoustic instability is affected bymore » the magnetic field strength much more than that of the filamentation instability in the low frequency range. The external magnetic field facilitates the development of the ion-acoustic instability. It is also shown that the filamentation is the dominant instability only for the high value of drift velocity.« less

Diffuse phase ferroelectric vs. Polomska transition in (1-x) BiFeO3-(x) Ba Zr0.025Ti0.975O3 (0.1 ≤ x ≤ 0.3) solid solutions

NASA Astrophysics Data System (ADS)

Jha, Pardeep K.; Jha, Priyanka A.; Singh, Vikash; Kumar, Pawan; Asokan, K.; Dwivedi, R. K.

2015-01-01

Investigations on the solid solutions (1-x) BiFeO3 - (x) Ba Zr0.025Ti0.975O3 (0.1 ≤ x ≤ 0.3) in the temperature range 300-750 K show colossal permittivity behavior and the occurrence of diffuse phase ferroelectric transition along with frequency dependent anomaly which disappears at temperature ˜450 K. For x = 0.3, these anomalies have been verified through differential scanning calorimetry and dielectric/impedance/conductivity measurements. The occurrence of peak in pyrocurrent (dPs/dT) vs. T plots also supports phase transition. With the increasing x, transition temperature decreases and diffusivity increases. This anomaly is absent at high frequencies (>100 kHz) in conductivity plots, indicating Polomska like surface phase transition, which is supported by modulus study.

Dielectric Properties of Boron Nitride-Ethylene Glycol (BN-EG) Nanofluids

NASA Astrophysics Data System (ADS)

Fal, Jacek; Cholewa, Marian; Gizowska, Magdalena; Witek, Adam; ŻyŁa, GaweŁ

2017-02-01

This paper presents the results of experimental investigation of the dielectric properties of ethylene glycol (EG) with various load of boron nitride (BN) nanoparticles. The nanofuids were prepared by using a two-step method on the basis of commercially available BN nanoparticles. The measurements were carried out using the Concept 80 System (NOVOCONTROL Technologies GmbH & Co. KG, Montabaur, Germany) in a frequency range from 10 Hz to 10 MHz and temperatures from 278.15 K to 328.15 K. The frequency-dependent real (ɛ ^' }) and imaginary (ɛ ^' ' }) parts of the complex permittivity (ɛ ^*) and the alternating current (AC) conductivity are presented. Also, the effect of temperature and mass concentrations on the dielectric properties of BN-EG nanofluids are demonstrated. The results show that the most significant increase can be achieved for 20 wt.% of BN nanoparticles at 283.15 K and 288.15 K, that is eleven times larger than in the case of pure EG.

Polar fluctuations in Mn substituted KTaO{sub 3} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Axelsson, Anna-Karin; Pan Yuya; Valant, Matjaz

2010-09-15

Polar fluctuations were found in KTaO{sub 3} when K{sup +} was substituted with Mn{sup 2+} on the A-site. The temperature dependence of the real part of the dielectric permittivity of (K{sub 1-2x}Mn{sub x{open_square}x})TaO{sub 3} ceramics (x=0-0.05) shows a diffuse maximum between 50-100 K in the frequency range 10{sup 2}-10{sup 6} Hz, shifting to higher temperature with increasing frequency and Mn content. The results are analyzed using a modified Curie-Weiss law, the Cole-Cole equation and the Arrhenius law. Here it is suggested that the observed relaxor-type dielectric behavior is attributed to the formation of electric dipoles originating from two distinct sources;more » one from an atomic off-center position when Mn{sup 2+} substitutes for K{sup +} and one from the anion deficiencies formed by these aliovalent substitutions.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Yongli; Wang, Xianjie; Sui, Yu

Here in this article, we investigated the dielectric properties of (In + Nb) co-doped rutile TiO 2 single crystal and polycrystalline ceramics. Both of them showed colossal, up to 10 4, dielectric permittivity at room temperature. The single crystal sample showed one dielectric relaxation process with a large dielectric loss. The voltage-dependence of dielectric permittivity and the impedance spectrum suggest that the high dielectric permittivity of single crystal originated from the surface barrier layer capacitor (SBLC). The impedance spectroscopy at different temperature confirmed that the (In+Nb) co-doped rutile TiO 2 polycrystalline ceramic had semiconductor grains and insulating grain boundaries, andmore » that the activation energies were calculated to be 0.052 eV and 0.35 eV for grain and grain boundary, respectively. The dielectric behavior and impedance spectrum of the polycrystalline ceramic sample indicated that the internal barrier layer capacitor (IBLC) mode made a major contribution to the high ceramic dielectric permittivity, instead of the electron-pinned defect-dipoles.« less

Dielectric properties and the monoclinictriclinic inversion in albite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, P.; Duba, A.; Piwinskii, A.J.

1976-12-01

Dielectric properties (epsilon', real part of complex permittivity; epsilon'', imaginary part of complex permittivity; tan delta, loss tangent = epsilon''/epsilon') of single crystal Amelia albite have been measured parallel to the b-axis under controlled oxygen fugacity near the QFM buffer in the temperature range 1000 to 1373/sup 0/K at frequencies (..nu..) of 0.2 to 10 kHz. Plots of epsilon' and epsilon'' as a function of temperature exhibit minima which depend on time and ..nu.. in this albite. In addition, plots of tan delta as a function of temperature develop maxima which are also time-dependent. When epsilon', epsilon'', and tan deltamore » were investigated between 1220 and 1320/sup 0/K as a function of time, a break in these dielectric parameters with temperature was found. Epsilon' and epsilon'' increased with time above this break, while they decreased with time below the break. Values of loss tangent were also non-linear functions of temperature. Epsilon' and epsilon'' minima, tan delta maxima, and the temperature break in these dielectric properties were found to converge at approximately 1283/sup 0/K as time increases. Assuming that the epsilon' and epsilon'' increase and the tan delta decrease are the result of increasing disorder in this albite, these experimental data suggest that 1283 +- 20/sup 0/K is the temperature of the monoclinic-triclinic transition in this albite. This agrees well with electrical conductivity results which indicate 1253 +- 30/sup 0/K.« less

Au-Ag-Cu nano-alloys: tailoring of permittivity

NASA Astrophysics Data System (ADS)

Hashimoto, Yoshikazu; Seniutinas, Gediminas; Balčytis, Armandas; Juodkazis, Saulius; Nishijima, Yoshiaki

2016-04-01

Precious metal alloys enables new possibilities to tailor materials for specific optical functions. Here we present a systematic study of the effects of a nanoscale alloying on the permittivity of Au-Ag-Cu metals at 38 different atomic mixing ratios. The permittivity was measured and analyzed numerically by applying the Drude model. X-ray diffraction (XRD) revealed the face centered cubic lattice of the alloys. Both, optical spectra and XRD results point towards an equivalent composition-dependent electron scattering behavior. Correlation between the fundamental structural parameters of alloys and the resulting optical properties is elucidated. Plasmonic properties of the Au-Ag-Cu alloy nanoparticles were investigated by numerical simulations. Guidelines for designing plasmonic response of nano- structures and their patterns are presented from the material science perspective.

Thickness-dependent domain wall reorientation in 70/30 lead magnesium niobate- lead titanate thin films

DOE PAGES

Keech, Ryan; Morandi, Carl; Wallace, Margeaux; ...

2017-04-11

Continued reduction in length scales associated with many ferroelectric film-based technologies is contingent on retaining the functional properties as the film thickness is reduced. Epitaxial and polycrystalline lead magnesium niobate - lead titanate (70PMN-30PT) thin films were studied over the thickness range of 100-350 nm for the relative contributions to property thickness dependence from interfacial and grain boundary low permittivity layers. Epitaxial PMN-PT films were grown on SrRuO 3 /(001)SrTiO 3, while polycrystalline films with {001}-Lotgering factors >0.96 were grown on Pt/TiO 2/SiO 2/Si substrates via chemical solution deposition. Both film types exhibited similar relative permittivities of ~300 at highmore » fields at all measured thicknesses with highly crystalline electrode/dielectric interfaces. These results, with the DC-biased and temperature dependent dielectric characterization, suggest irreversible domain wall mobility is the major contributor to the overall dielectric response and its thickness dependence. In epitaxial films, the irreversible Rayleigh coefficients reduced 85% upon decreasing thickness from 350 to 100 nm. The temperature at which a peak in the relative permittivity is observed was the only measured small signal quantity which was more thickness dependent in polycrystalline than epitaxial films. This is attributed to the relaxor nature present in the films, potentially stabilized by defect concentrations, and/or chemical inhomogeneity. Finally, the effective interfacial layers are found to contribute to the measured thickness dependence in the longitudinal piezoelectric coefficient.« less

Microfluidic-based Broadband Measurements of Fluid Permittivity and Permeability to 100 GHz

NASA Astrophysics Data System (ADS)

Little, Charles A. E.

This dissertation concerns the development of unique microfluidic microwave devices and associated microwave calibrations to quantitatively extract the broadband permittivity and permeability of fluids between 100 kHz and 110 GHz. The devices presented here consist of SU-8- and PDMS-based microfluidic channels integrated lithographically with coplanar waveguides (CPWs), measured via an external vector network analyzer (VNA). By applying our hybrid set of microwave calibrations to the raw data we extract distributed circuit parameters, representative of the electromagnetic response of the microfluidic channel. We then correlate these parameters to the permittivity and permeability of the fluid within the channels. We are primarily focused on developing devices, calibrations, and analyses to characterize various chemical and biological systems. The small fluid volumes and overall scale of our devices lends the technique to point-of-care blood and cell analysis, as well as to the analysis of high-value chemicals. Broadband microwave microfluidics is sensitive to three primary categories of phenomena: Ionic, dipolar, and magnetic resonances. All three can occur in complex fluids such as blood, proteins and particle suspensions. In order to make quantitative measurements, we need to be able to model and separate all three types of responses. Here we first measure saline solutions (NaCl and water) as an ideal system to better understanding both the ionic and dipolar response. Specifically, we are targeting the electrical double-layer (EDL) response, an ionic effect, which dominates over the intrinsic fluid response at lower frequencies. We have found that the EDL response for saline obeys a strict Debye-type relaxation model, the frequency response of which is dependent solely on the conductivity of the solution. To develop a better understanding of the magnetic response, we first measure magnetic nanoparticles; showing it is possible to detect the magnetic resonances of magnetic nanoparticle in a fluid environment using the broad-band approach, and that the response matches cavity-based measurements. In addition, we demonstrate the complicated intermixing that occurs between magnetic and electrical responses in CPW-type measurements through both numerical modeling, and empirical measurements of impeded embedded permalloy devices.

Frequency-Temperature Compensation Techniques for High-Q Microwave Resonators

NASA Astrophysics Data System (ADS)

Hartnett, John G.; Tobar, Michael E.

Low-noise high-stability resonator oscillators based on high-Q monolithic sapphire ``Whispering Gallery'' (WG)-mode resonators have become important devices for telecommunication, radar and metrological applications. The extremely high quality factor of sapphire, of 2 x10^5 at room temperature, 5 x10^7 at liquid nitrogen temperature and 5 x10^9 at liquid helium temperature has enabled the lowest phase noise and highly frequency-stable oscillators in the microwave regime to be constructed. To create an oscillator with exceptional frequency stability, the resonator must have its frequency-temperature dependence annulled at some temperature, as well as a high quality factor. The Temperature Coefficient of Permittivity (TCP) for sapphire is quite large, at 10-100parts per million/K above 77K. This mechanism allows temperature fluctuations to transform to resonator frequency fluctuations.A number of research groups worldwide have investigated various methods of compensating the TCP of a sapphire dielectric resonator at different temperatures. The usual electromagnetic technique of annulment involves the use of paramagnetic impurities contributing an opposite temperature coefficient of the magnetic susceptibility to the TCP. This technique has only been realized successfully in liquid helium environments. Near 4K the thermal expansion and permittivity effects are small and only small quantities of the paramagnetic ions are necessary to compensate the mode frequency. Compensation is due to impurity ions that were incidentally left over from the manufacturing process.Recently, there has been an effort to dispense with the need for liquid helium and make a compact flywheel oscillator for the new generation of primary frequency standards such as the cesium fountain at the Laboratoire Primaire du Temps et des Fréquences (LPTF), France. To achieve the stability limit imposed by quantum projection noise requires that the local oscillator stability is of the order of 10^-14. Currently work is under way to achieve this goal in space-borne and mobile liquid-nitrogen-cooled systems. The work appears promising and, as at early 2000, the realization of this goal should not be far off.In this contribution we review techniques that cancel the TCP of sapphire and other dielectric resonators. Details of the temperature control system required to achieve current and target frequency stabilities are discussed.

Perforated-Layer Implementation Of Radio-Frequency Lenses

NASA Technical Reports Server (NTRS)

Dolgin, Benjamin P.

1996-01-01

Luneberg-type radio-frequency dielectric lenses made of stacked perforated circular dielectric sheets, according to proposal. Perforation pattern designed to achieve required spatial variation of permittivity. Consists of round holes distributed across face of each sheet in "Swiss-cheese" pattern, plus straight or curved slots that break up outer parts into petals in "daisy-wheel" pattern. Holes and slots made by numerically controlled machining.

Dielectric properties of agricultural products – fundamental principles, influencing factors, and measurement technirques. Chapter 4. Electrotechnologies for Food Processing: Book Series. Volume 3. Radio-Frequency Heating

USDA-ARS?s Scientific Manuscript database

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

Propagation of radio frequency waves through density fluctuations

NASA Astrophysics Data System (ADS)

Valvis, S. I.; Papagiannis, P.; Papadopoulos, A.; Hizanidis, K.; Glytsis, E.; Bairaktaris, F.; Zisis, A.; Tigelis, I.; Ram, A. K.

2017-10-01

On their way to the core of a tokamak plasma, radio frequency (RF) waves, excited in the vacuum region, have to propagate through a variety of density fluctuations in the edge region. These fluctuations include coherent structures, like blobs that can be field aligned or not, as well as turbulent and filamentary structures. We have been studying the effect of fluctuations on RF propagation using both theoretical (analytical) and computational models. The theoretical results are being compared with those obtained by two different numerical codes ``a Finite Difference Frequency Domain code and the commercial COMSOL package. For plasmas with arbitrary distribution of coherent and turbulent fluctuations, we have formulated an effective dielectric permittivity of the edge plasma. This permittivity tensor is then used in numerical simulations to study the effect of multi-scale turbulence on RF waves. We not only consider plane waves but also Gaussian beams in the electron cyclotron and lower hybrid range of frequencies. The analytical theory and results from simulations on the propagation of RF waves will be presented. Supported in part by the Hellenic National Programme on Controlled Thermonuclear Fusion associated with the EUROfusion Consortium and by DoE Grant DE-FG02-91ER-54109.

The observation of negative permittivity in stripe and bubble phases

NASA Astrophysics Data System (ADS)

Smet, Jurgen

The physics of itinerant two-dimensional electrons is by and large governed by repulsive Coulomb forces. However, cases exist where the interplay of attractive and repulsive interaction components may instigate spontaneous symmetry lowering and clustering of charges in geometric patterns such as bubbles and stripes, provided these interactions act on different length scales. The existence of these phases in higher Landau levels has so far been concluded from transport behavior. Here, we report surface acoustic wave experiments. They probe the permittivity at small wave vector. This technique offers true directionality, whereas in transport the current distribution is complex and strongly affected by the inhomogeneous density pattern. Outside the charge density wave regime, the measured permittivity is always positive. However, negative permittivity is observed in the bubble phase irrespective of the propagation direction. For the stripe phase the permittivity takes on both positive as well as negative values depending on the propagation direction. This confirms the stripe phase to be a strongly anisotropic medium. The observation of negative permittivity is considered an immediate consequence of the exchange related attractive interaction. It makes charge clustering favorable in higher Landau levels where the repulsive direct Coulomb interaction acts on a longer length scale and is responsible for a negative compressibility of the electronic system. This work has been carried out with B. Friess, K. von Klitzing (MPI-FKF), Y. Peng, F. von Oppen (FU Berlin), B. Rosenow (Uni Leipzig) and V. Umansky (Weizmann Institute of Science).

Patterned Ferroelectric Films for Tunable Microwave Devices

NASA Technical Reports Server (NTRS)

Miranda, Felix A.; Mueller, Carl H.

2008-01-01

Tunable microwave devices based on metal terminals connected by thin ferroelectric films can be made to perform better by patterning the films to include suitably dimensioned, positioned, and oriented constrictions. The patterns can be formed during fabrication by means of selective etching processes. If the width of the ferroelectric film in such a device is reduced at one or more locations, then both the microwave field and any applied DC bias (tuning) electric field become concentrated at those locations. The magnitudes of both the permittivity and the dielectric loss of a ferroelectric material are reduced by application of a DC field. Because the concentration of the DC field in the constriction(s) magnifies the permittivity- and loss-reducing effects of the applied DC voltage, the permittivity and dielectric loss in the constriction(s) are smaller in the constriction(s) than they are in the wider parts of the ferroelectric film. Furthermore, inasmuch as displacement current must flow through either the constriction(s) or the low-loss dielectric substrate, the net effect of the constriction(s) is equivalent to that of incorporating one or more low-loss, low-permittivity region(s) in series with the high-loss, high-permittivity regions. In a series circuit, the properties of the low-capacitance series element (in this case, the constriction) dominate the overall performance. Concomitantly, the capacitance between the metal terminals is reduced. By making the capacitance between the metal terminals small but tunable, a constriction increases the upper limit of the frequency range amenable to ferroelectric tuning. The present patterning concept is expected to be most advantageous for devices and circuits that must operate at frequencies from about 4 to about 60 GHz. A constriction can be designed such that the magnitude of the microwave electric field and the effective width of the region occupied by the microwave electric field become functions of the applied DC electric field, so that tunability is enhanced. It should even be possible to design the constriction to obtain a specific tuning-versus-voltage profile.

Precise measurement of dielectric anisotropy in ice Ih at 39 GHz

NASA Astrophysics Data System (ADS)

Matsuoka, Takeshi; Fujita, Shuji; Morishima, Shigenori; Mae, Shinji

1997-03-01

The dielectric permittivities parallel and perpendicular to the c axis (optic axis) of ice Ih were measured using an open resonator at 39 GHz in the temperature range 194-262 K. The dielectric anisotropy in ice at microwave frequencies is important for understanding remote sensing data in polar regions, obtained by ice radar and satellite-born microwave radar and radiometer. The measured samples were natural single-crystal ice collected from Mendenhall Glacier, Alaska. A very precise measurement was achieved by detecting two resonant peaks, one from the ordinary component and the other from the extraordinary component, simultaneously, from one sample. The real part of dielectric anisotropy, Δɛ'=ɛ∥c'-ɛ⊥c', at 39 GHz was 0.0339±0.0007 (1.07%±0.02%) at 252 K and slightly depended on temperature. Reference measurements at 1 MHz using parallel plate electrodes were also carried out. The measured dielectric anisotropy at microwave frequencies agrees very well with the value at 1 MHz. The absolute values of ɛ∥c' and ɛ⊥c' at 39 GHz were, respectively, smaller than those at 1 MHz and the difference was about 0.044 at 252 K. The results suggest that a small dispersion exists between GHz and MHz frequencies, but there is no frequency dependence in the value of anisotropy.

Difference and similarity of dielectric relaxation processes among polyols

NASA Astrophysics Data System (ADS)

Minoguchi, Ayumi; Kitai, Kei; Nozaki, Ryusuke

2003-09-01

Complex permittivity measurements were performed on sorbitol, xylitol, and sorbitol-xylitol mixture in the supercooled liquid state in an extremely wide frequency range from 10 μHz to 500 MHz at temperatures near and above the glass transition temperature. We determined detailed behavior of the relaxation parameters such as relaxation frequency and broadening against temperature not only for the α process but also for the β process above the glass transition temperature, to the best of our knowledge, for the first time. Since supercooled liquids are in the quasi-equilibrium state, the behavior of all the relaxation parameters for the β process can be compared among the polyols as well as those for the α process. The relaxation frequencies of the α processes follow the Vogel-Fulcher-Tammann manner and the loci in the Arrhenius diagram are different corresponding to the difference of the glass transition temperatures. On the other hand, the relaxation frequencies of the β processes, which are often called as the Johari-Goldstein processes, follow the Arrhenius-type temperature dependence. The relaxation parameters for the β process are quite similar among the polyols at temperatures below the αβ merging temperature, TM. However, they show anomalous behavior near TM, which depends on the molecular size of materials. These results suggest that the origin of the β process is essentially the same among the polyols.

Terahertz transmission properties of a triadic-Cantor-set photonic crystal containing a semiconductor

NASA Astrophysics Data System (ADS)

King, Tzu-Chyang; Liu, Chi-Chung; Huang, Chih-Hsi; Wu, Chien-Jang

2016-08-01

Terahertz transmission properties of a stage 3 triadic-Cantor-set photonic crystal (S3 TCS PC) containing a semiconductor of n-InSb are theoretically investigated. With the resonant frequency in the permittivity function of n-InSb, transmission responses can be classified as three regions. In the two regions with frequencies well above and below the resonant frequency, the permittivity functions are nearly a positive constant and n-InSb is dielectric-like. For these two regions, transmittance response of S3 TCS PC at a given number of periods Np reveals that, within a photonic band gap, there are two groups of defect modes with numbers of Np and Np-1, respectively. Defect modes are shown to be blue-shifted as the angle of incidence increases for both TE and TM waves. Additionally, adjusting the layer thickness enables us to control mode positions for the group of (Np-1)-mode, but the one with Np-mode is not able to be controlled. In a region of 5.1-6.2 THz, where the loss is large, there also are many transmission modes.

High Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring and Verification Efforts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Ki Ha; Becker, Alex; Framgos, William

1999-06-01

Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data can bemore » mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately imaging the electrical conductivity and dielectric permittivity of the shallow subsurface using the plane wave impedance approach. Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.« less

High-Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring and Verification Efforts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Ki Ha; Becker, Alex; Tseng, Hung-Wen

2002-11-20

Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic (EM) measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data canmore » be mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using the EM impedance approach (Frangos, 2001; Lee and Becker, 2001; Song et al., 2002). Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.« less

High-Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring, and Verification Efforts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Ki Ha; Becker, Alex

2000-06-01

Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data can bemore » mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately imaging the electrical conductivity and dielectric permittivity of the shallow subsurface using the plane wave impedance approach (Song et al., 1997). Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.« less

High-Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring and Verification Efforts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Ki Ha; Becker, Alex; Tseng, Hung-Wen

2001-06-10

Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic (EM) measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data canmore » be mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using the EM impedance approach (Frangos, 2001; Lee and Becker, 2001). Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.« less

Effect of medium electrophysical parameters and their temperature dependences on wideband electromagnetic pulse propagation

NASA Astrophysics Data System (ADS)

Volkomirskaya, L. B.; Gulevich, O. A.; Reznikov, A. E.

2017-03-01

The dielectric permittivity of fiery spoil tips (Shakhty town, Rostov Region) is studied with the use of a GROT 12E remote-controlled ground-penetrating radar (GPR). An anomalous zone in a combustion source is shown to be clearly pronounced in GPR data due to the temperature dependence of the dielectric permittivity of these spoil tips. To substantiate this statement, the GPR data are compared with direct measurements of soil temperatures at depths from 1.5 to 2.5 m. The experimental results are compared with the variable spectral range of a GPR sounding pulse. GPR is shown to be a promising tool for the mapping of temperature-contrast underground objects.

Relative permittivity and Hubbard U of pentacene extracted from scanning tunneling microscopy studies of p-doped films

NASA Astrophysics Data System (ADS)

Ha, Sieu D.; Qi, Yabing; Kahn, Antoine

2010-08-01

Temperature-dependent I- V measurements determine that pentacene is effectively p-doped by tetrafluoro-tetracyanoquinodimethane (F 4-TCNQ). It has been shown by scanning tunneling microscopy (STM) that the donated hole is localized by the ionized dopant counter potential, and that the hole can be visualized [4]. Here, it is argued that the effect of the localized hole on STM images should depend on distance as 1/ ɛr, as per the Coulomb potential. By fitting line profiles of localized hole features to the Coulomb potential, it is shown that approximate values for the relative permittivity and Hubbard U of pentacene can be extracted.

Au-Ag-Cu nano-alloys: tailoring of permittivity

PubMed Central

Hashimoto, Yoshikazu; Seniutinas, Gediminas; Balčytis, Armandas; Juodkazis, Saulius; Nishijima, Yoshiaki

2016-01-01

Precious metal alloys enables new possibilities to tailor materials for specific optical functions. Here we present a systematic study of the effects of a nanoscale alloying on the permittivity of Au-Ag-Cu metals at 38 different atomic mixing ratios. The permittivity was measured and analyzed numerically by applying the Drude model. X-ray diffraction (XRD) revealed the face centered cubic lattice of the alloys. Both, optical spectra and XRD results point towards an equivalent composition-dependent electron scattering behavior. Correlation between the fundamental structural parameters of alloys and the resulting optical properties is elucidated. Plasmonic properties of the Au-Ag-Cu alloy nanoparticles were investigated by numerical simulations. Guidelines for designing plasmonic response of nano- structures and their patterns are presented from the material science perspective. PMID:27118459

Refinement of the theory for extracting cell dielectric properties from dielectrophoresis and electrorotation experiments.

PubMed

Lei, U; Sun, Pei-Hou; Pethig, Ronald

2011-12-01

A modified theory is proposed for extracting cell dielectric properties from the peak frequency measurement of electrorotation (ER) and the crossover frequency measurement of dielectrophoresis (DEP). Current theory in the literature is based on the low frequency (DC) approximations for the equivalent cell permittivity and conductivity, which are valid when the measurements are performed in a medium with conductivity less than 1 mS/m. The present theory extracts the cell properties through optimizing an expression for the medium conductivity in terms of the peak ER, or DEP crossover, frequency according to its definition using full expressions of equivalent cell permittivity and conductivity. Various levels of approximation of the theory are proposed and discussed through a scaling analysis. The present theory can extract both membrane and interior properties from the low and the high peak ER, or DEP crossover, frequencies for any medium conductivity provided the peak ER, or DEP crossover, frequency exists. It can be reduced to the linear theory for the low peak ER and DEP crossover frequencies in the literature when the medium conductivity is less than 10 mS/m. However, we can determine the membrane capacitance and conductance via the slope and intercept, respectively, of the straight line fitting of the ER peak and DEP frequency against medium conductivity data according to the linear theory only when the intercept dominates the experimental uncertainty, which occurs when the medium conductivity is less than 1 mS/m in practice.

Ultraslow dielectric relaxation process in supercooled polyhydric alcohols

NASA Astrophysics Data System (ADS)

Yomogida, Yoshiki; Minoguchi, Ayumi; Nozaki, Ryusuke

2006-04-01

Complex permittivity was obtained on glycerol, xylitol, sorbitol and sorbitol-xylitol mixtures in the supercooled liquid state in the frequency range between 10μHz and 500MHz at temperatures near and above the glass transition temperature. For all the materials, a dielectric relaxation process was observed in addition to the well-known structural α and Johari-Goldstein β relaxation process [G. P. Johari and M. Goldstein, J. Chem. Phys. 53, 2372 (1970)]. The relaxation time for the new process is always larger than that for the α process. The relaxation time shows non-Arrhenius temperature dependence with correlation to the behavior of the α process and it depends on the molecular size systematically. The dielectric relaxation strength for the new process shows the effect of thermal history and decreases exponentially with time at a constant temperature. It can be considered that a nonequilibrium dynamics causes the new process.

Photonic band gap spectra in Octonacci metamaterial quasicrystals

NASA Astrophysics Data System (ADS)

Brandão, E. R.; Vasconcelos, M. S.; Albuquerque, E. L.; Fulco, U. L.

2017-02-01

In this work we study theoretically the photonic band gap spectra for a one-dimensional quasicrystal made up of SiO2 (layer A) and a metamaterial (layer B) organized following the Octonacci sequence, where its nth-stage Sn is given by the inflation rule Sn =Sn - 1Sn - 2Sn - 1 for n ≥ 3 , with initial conditions S1 = A and S2 = B . The metamaterial is characterized by a frequency dependent electric permittivity ε(ω) and magnetic permeability μ(ω) . The polariton dispersion relation is obtained analytically by employing a theoretical calculation based on a transfer-matrix approach. A quantitative analysis of the spectra is then discussed, stressing the distribution of the allowed photonic band widths for high generations of the Octonacci structure, which depict a self-similar scaling property behavior, with a power law depending on the common in-plane wavevector kx .

Nanotwin and phase transformation in tetragonal Pb(Fe1/2Nb1/2)1-xTixO3 single crystal

NASA Astrophysics Data System (ADS)

Tu, C.-S.; Tseng, C.-T.; Chien, R. R.; Schmidt, V. Hugo; Hsieh, C.-M.

2008-09-01

This work is a study of phase transformation in (001)-cut Pb(Fe1/2Nb1/2)1-xTixO3 (x =48%) single crystals by means of dielectric permittivity, domain structure, and in situ x-ray diffraction. A first-order T(TNT)-C(TNT) phase transition was observed at the Curie temperature TC≅518 K upon zero-field heating. T, TNT, and C are tetragonal, tetragonal nanotwin, and cubic phases, respectively. T(TNT) and C(TNT) indicate that minor TNT domains reside in the T and C matrices. Nanotwins, which can cause broad diffraction peak, remain above TC≅518 K and give an average microscopic cubic symmetry in the polarizing microscopy. Colossal dielectric permittivity (>104) was observed above room temperature with strong frequency dispersion. This study suggests that nanotwins can play an important role in relaxor ferroelectric crystals while phase transition takes place. The Fe ion is a potential candidate as a B-site dopant for enhancing dielectric permittivity.

High-performance gap-closing vibrational energy harvesting using electret-polarized dielectric oscillators

NASA Astrophysics Data System (ADS)

Feng, Yue; Yu, Zejie; Han, Yanhui

2018-01-01

In conventional gap-closing electret-biased electrostatic energy harvesting (EEEH) schemes, electrets with a very low ratio of electret thickness to permittivity are in great demand to allow the attainment of high power output. However, in practice, pursuing such a low ratio introduces unwanted burdens on the electret stability and therefore the reliability of the EEEH devices. In this paper, we propose a dielectric-oscillator-based electrostatic EH (DEEH) scheme as an alternative approach to harvesting electret-biased electrostatic energy. This approach permits the fabrication of an electret-free closed EH circuit. The DEEH architecture directly collects the electrical energy exclusively through the oscillating dielectric body and thus completely circumvents the restrictions imposed by the electret parameters (thickness and permittivity) on power generation. Significantly, without considering the electret thickness and permittivity, both theoretical analysis and experiments have verified the effectiveness of this DEEH strategy, and a high figure of merit (on the order of 10-8 mW cm-2 V-2 Hz-1) was achieved for low-frequency movements.

Agricultural wastes as a resource of raw materials for developing low-dielectric glass-ceramics

PubMed Central

Danewalia, Satwinder Singh; Sharma, Gaurav; Thakur, Samita; Singh, K.

2016-01-01

Agricultural waste ashes are used as resource materials to synthesize new glass and glass-ceramics. The as-prepared materials are characterized using various techniques for their structural and dielectric properties to check their suitability in microelectronic applications. Sugarcane leaves ash exhibits higher content of alkali metal oxides than rice husk ash, which reduces the melting point of the components due to eutectic reactions. The addition of sugarcane leaves ash in rice husk ash promotes the glass formation. Additionally, it prevents the cristobalite phase formation. These materials are inherently porous, which is responsible for low dielectric permittivity i.e. 9 to 40. The presence of less ordered augite phase enhances the dielectric permittivity as compared to cristobalite and tridymite phases. The present glass-ceramics exhibit lower losses than similar materials synthesized using conventional minerals. The dielectric permittivity is independent to a wide range of temperature and frequency. The glass-ceramics developed with adequately devitrified phases can be used in microelectronic devices and other dielectric applications. PMID:27087123

Optimum discharge energy density at room temperature in relaxor K1/2Bi1/2TiO3 for green energy harvesting

NASA Astrophysics Data System (ADS)

Banerjee, Krishnarjun; Asthana, Saket; Karuna Kumari, P.; Niranjan, Manish K.

2018-03-01

Lead-free polycrystalline K1/2Bi1/2TiO3 was prepared by the solid state reaction method. Experimentally observed frequencies of Raman modes signified its tetragonal phase, and matched reasonably well with theoretically calculated values. The relaxor nature of this material was observed in the temperature-dependent real part of the permittivity and dielectric loss curve. The value of the degree of diffuseness (1.99) was estimated from the modified Curie-Weiss law confirmed its relaxor behavior. The validation of this behavior was justified by the Vogel-Fülcher relation. The shoulder in the imaginary part of the modulus (M″) and permittivity (ɛ″) spectra revealed the presence of polar nano regions (PNRs). The evidence of PNRs was detectable above freezing temperatures, and became weaker when the temperature exceeded T m (temperature at the maximum of the dielectric constant). The electric field-induced polarization and strain curve showed the stabilization of the long-range ferroelectric order of the specimen at room temperature. Moreover, the discharge energy density and strain were 0.46 J cm-3 and 0.12%, respectively, at the maximum application of the electric field of 115 kV cm-1 at room temperature.

Novel Dual-band Band-Pass Filters Based on Surface Plasmon Polariton-like Propagation Induced by Structural Dispersion of Substrate Integrated Waveguide.

PubMed

Cselyuszka, Norbert; Sakotic, Zarko; Kitic, Goran; Crnojevic-Bengin, Vesna; Jankovic, Nikolina

2018-05-29

In this paper, we present two novel dual-band bandpass filters based on surface plasmon polariton-like (SPP-like) propagation induced by structural dispersion of substrate integrated waveguide (SIW). Both filters are realized as a three-layer SIW where each layer represents a sub-SIW structure with intrinsic effective permittivity that depends on its width and filling dielectric material. The layers are designed to have effective permittivities of opposite signs in certain frequency ranges, which enables SPP-like propagation to occur at their interfaces. Since three layers can provide two distinct SPP-like propagations, the filters exhibit dual-band behaviour. A detailed theoretical and numerical analysis and numerical optimization have been used to design the filters, which were afterwards fabricated using standard printed circuit board technology. The independent choice of geometrical parameters of sub-SIWs and/or the corresponding dielectric materials provide a great freedom to arbitrarily position the passbands in the spectrum, which is a significant advantage of the proposed filters. At the same time, they meet the requirements for low-cost low-profile configuration since they are realized as SIW structures, as well as for excellent in-band characteristics and selectivity which is confirmed by the measurement results.

ClotChip: A Microfluidic Dielectric Sensor for Point-of-Care Assessment of Hemostasis.

PubMed

Maji, Debnath; Suster, Michael A; Kucukal, Erdem; Sekhon, Ujjal D S; Gupta, Anirban Sen; Gurkan, Umut A; Stavrou, Evi X; Mohseni, Pedram

2017-12-01

This paper describes the design, fabrication, and testing of a microfluidic sensor for dielectric spectroscopy of human whole blood during coagulation. The sensor, termed ClotChip, employs a three-dimensional, parallel-plate, capacitive sensing structure with a floating electrode integrated into a microfluidic channel. Interfaced with an impedance analyzer, the ClotChip measures the complex relative dielectric permittivity, ϵ r , of human whole blood in the frequency range of 40 Hz to 100 MHz. The temporal variation in the real part of the blood dielectric permittivity at 1 MHz features a time to reach a permittivity peak, , as well as a maximum change in permittivity after the peak, , as two distinct parameters of ClotChip readout. The ClotChip performance was benchmarked against rotational thromboelastometry (ROTEM) to evaluate the clinical utility of its readout parameters in capturing the clotting dynamics arising from coagulation factors and platelet activity. exhibited a very strong positive correlation ( r = 0.99, p < 0.0001) with the ROTEM clotting time parameter, whereas exhibited a strong positive correlation (r = 0.85,  p < 0.001) with the ROTEM maximum clot firmness parameter. This paper demonstrates the ClotChip potential as a point-of-care platform to assess the complete hemostatic process using <10 μL of human whole blood.

Metamaterial for Radar Frequencies

DTIC Science & Technology

2012-09-01

Circuit Board RAM Radar Absorbing Material RCS Radar Cross Section SNR Signal-to-Noise Ratio SNG Single-Negative SRR Split Ring Resonator...although some can be single-negative ( SNG ). DNG refers to material with simultaneous negative real parts of the permittivity r  and permeability

A general framework for numerical simulation of improvised explosive device (IED)-detection scenarios using density functional theory (DFT) and terahertz (THz) spectra.

PubMed

Shabaev, Andrew; Lambrakos, Samuel G; Bernstein, Noam; Jacobs, Verne L; Finkenstadt, Daniel

2011-04-01

We have developed a general framework for numerical simulation of various types of scenarios that can occur for the detection of improvised explosive devices (IEDs) through the use of excitation using incident electromagnetic waves. A central component model of this framework is an S-matrix representation of a multilayered composite material system. Each layer of the system is characterized by an average thickness and an effective electric permittivity function. The outputs of this component are the reflectivity and the transmissivity as functions of frequency and angle of the incident electromagnetic wave. The input of the component is a parameterized analytic-function representation of the electric permittivity as a function of frequency, which is provided by another component model of the framework. The permittivity function is constructed by fitting response spectra calculated using density functional theory (DFT) and parameter adjustment according to any additional information that may be available, e.g., experimentally measured spectra or theory-based assumptions concerning spectral features. A prototype simulation is described that considers response characteristics for THz excitation of the high explosive β-HMX. This prototype simulation includes a description of a procedure for calculating response spectra using DFT as input to the Smatrix model. For this purpose, the DFT software NRLMOL was adopted. © 2011 Society for Applied Spectroscopy

Magnetoelectric properties of Co-doped BiFeO3 nanoparticles

NASA Astrophysics Data System (ADS)

Shrimali, V. G.; Rathod, K. N.; Dhruv, Davit; Zankat, Alpa; Sagapariya, Khushal; Solanki, Sapana; Solanki, P. S.; Shah, N. A.; Kataria, B. R.

2018-05-01

The magnetoelectric (ME) properties of sol-gel grown BiFe0.95Co0.05O3 (BFCO) nanoceramics, with different sizes, were investigated at room-temperature. X-ray diffraction (XRD) measurement was performed to investigate structural properties of the samples understudy. Magnetic field-dependent dielectric permittivity has been systematically investigated in the frequency range of 20 Hz to 1 MHz. To ensure the origin of magnetodielectric response, the magnetoimpedance (MI) spectroscopy was adopted using equivalent circuit model. The a.c. conductivity was found to obey the Jonscher’s universal power law. The modifications in spiral spin structure in the BFCO nanoparticles with size less than ˜62 nm significantly affect the ME coupling parameters.

Variation of the electric properties along the diaphysis of bovine femoral bone.

PubMed

De Mercato, G; García Sánchez, F J

1991-07-01

A preliminary study is presented of the variability of the electric properties, in the axial, tangential and radial directions, as a function of position in the diaphysis of a femoral bovine bone. The measurements were carried out at three frequencies: 100 Hz, 10 kHz and 1 MHz. It is shown that both the conductivity and the permittivity exhibit significant variations along the diaphysis, and increase in magnitude towards the epiphyses. From this study, the variation of the electric properties cannot be clearly and directly ascribed to the longitudinal variability of the total volumetric fluid content of the bone. The results reflect the orthotropic nature of the electric properties, at any given location, and indicate a position-dependent tendency towards axis symmetry.

Giant Linear Nonreciprocity, Zero Reflection, and Zero Band Gap in Equilibrated Space-Time-Varying Media

NASA Astrophysics Data System (ADS)

Taravati, Sajjad

2018-06-01

This article presents a class of space-time-varying media with giant linear nonreciprocity, zero space-time local reflections, and zero photonic band gap. This is achieved via equilibrium in the electric and magnetic properties of unidirectionally space-time-modulated media. The enhanced nonreciprocity is accompanied by a larger sonic regime interval which provides extra design freedom for achieving strong nonreciprocity by a weak pumping strength. We show that the width of photonic band gaps in general periodic space-time permittivity- and permeability-modulated media is proportional to the absolute difference between the electric and magnetic pumping strengths. We derive a rigorous analytical solution for investigation of wave propagation and scattering from general periodic space-time permittivity- and permeability-modulated media. In contrast with weak photonic transitions, from the excited mode to its two adjacent modes, in conventional space-time permittivity-modulated media, in an equilibrated space-time-varying medium, strong photonic transitions occur from the excited mode to its four adjacent modes. We study the enhanced nonreciprocity and zero band gap in equilibrated space-time-modulated media by analysis of their dispersion diagrams. In contrast to conventional space-time permittivity-modulated media, equilibrated space-time media exhibit different phase and group velocities for forward and backward harmonics. Furthermore, the numerical simulation scheme of general space-time permittivity- and permeability-modulated media is presented, which is based on the finite-difference time-domain technique. Our analytical and numerical results provide insights into general space-time refractive-index-modulated media, paving the way toward optimal isolators, nonreciprocal integrated systems, and subharmonic frequency generators.

Influence of permittivity on gradient force exerted on Mie spheres.

PubMed

Chen, Jun; Li, Kaikai; Li, Xiao

2018-04-01

In optical trapping, whether a particle could be stably trapped into the focus region greatly depends on the strength of the gradient force. Individual theoretical study on gradient force exerted on a Mie particle is rare because the mathematical separation of the gradient force and the scattering force in the Mie regime is difficult. Based on the recent forces separation work by Du et al. [Sci. Rep.7, 18042 (2017)SRCEC32045-232210.1038/s41598-017-17874-1], we investigate the influence of permittivity (an important macroscopic physical quantity) on the gradient force exerted on a Mie particle by cooperating numerical calculation using fast Fourier transform and analytical analysis using multipole expansion. It is revealed that gradient forces exerted on small spheres are mainly determined by the electric dipole moment except for certain permittivity with which the real part of polarizability of the electric dipole approaches zero, and gradient forces exerted on larger spheres are complex because of the superposition of the multipole moments. The classification of permittivity corresponding to different varying tendencies of gradient forces exerted on small spheres or larger Mie particles are illustrated. Absorption of particles favors the trapping of small spheres by gradient force, while it is bad for the trapping of larger particles. Moreover, the absolute values of the maximal gradient forces exerted on larger Mie particles decline greatly versus the varied imaginary part of permittivity. This work provides elaborate investigation on the different varying tendencies of gradient forces versus permittivity, which favors more accurate and free optical trapping.

FDTD Simulation on Terahertz Waves Propagation Through a Dusty Plasma

NASA Astrophysics Data System (ADS)

Wang, Maoyan; Zhang, Meng; Li, Guiping; Jiang, Baojun; Zhang, Xiaochuan; Xu, Jun

2016-08-01

The frequency dependent permittivity for dusty plasmas is provided by introducing the charging response factor and charge relaxation rate of airborne particles. The field equations that describe the characteristics of Terahertz (THz) waves propagation in a dusty plasma sheath are derived and discretized on the basis of the auxiliary differential equation (ADE) in the finite difference time domain (FDTD) method. Compared with numerical solutions in reference, the accuracy for the ADE FDTD method is validated. The reflection property of the metal Aluminum interlayer of the sheath at THz frequencies is discussed. The effects of the thickness, effective collision frequency, airborne particle density, and charge relaxation rate of airborne particles on the electromagnetic properties of Terahertz waves through a dusty plasma slab are investigated. Finally, some potential applications for Terahertz waves in information and communication are analyzed. supported by National Natural Science Foundation of China (Nos. 41104097, 11504252, 61201007, 41304119), the Fundamental Research Funds for the Central Universities (Nos. ZYGX2015J039, ZYGX2015J041), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20120185120012)

Enhanced Microwave Absorption Properties of Carbon Black/Silicone Rubber Coating by Frequency-Selective Surface

NASA Astrophysics Data System (ADS)

Yang, Zhaoning; Luo, Fa; Gao, Lu; Qing, Yuchang; Zhou, Wancheng; Zhu, Dongmei

2016-10-01

A square frequency-selective surface (FSS) design has been employed to improve the microwave absorption properties of carbon black/silicone rubber (CBSR) composite coating. The FSS is placed on the surface of the CBSR coating. The effects of FSS design parameters on the microwave absorption properties of the CBSR coating have been investigated, including the size and period of the FSS design, and the thickness and permittivity of the coating. Simulation results indicate that the absorption peak for the CBSR coating alone is related to its thickness and electromagnetic parameters, while the combination of the CBSR coating with a FSS can exhibit a new absorption peak in the reflection curve; the frequency of the new absorption peak is determined by the resonance of the square FSS design and tightly depends on the size of the squares, with larger squares in the FSS design leading to a lower frequency of the new absorption peak. The enhancement of the absorption performance depends on achievement of a new absorption peak using a suitable size and period of the FSS design. In addition, the FSS design has a stable frequency response for both transverse electromagnetic (TE) and transverse magnetic (TM) polarizations as the incident angle varies from 0° to 40°. The optimized results indicate that the bandwidth with reflection loss below -5 dB can encompass the whole frequency range from 8 GHz to 18 GHz for thickness of the CBSR coating of only 1.8 mm. The simulation results are confirmed by experiments.

Surface-PlasmonoDielectric-polaritonic devices and systems

DOEpatents

None, None

2013-06-25

There is provided a structure for supporting propagation of surface plasmon polaritons. The structure includes a plasmonic material region and a dielectric material region, disposed adjacent to a selected surface of the plasmonic material region. At least one of the plasmonic material region and the dielectric material region have a dielectric permittivity distribution that is specified as a function of depth through the corresponding material region. This dielectric permittivity distribution is selected to impose prespecified group velocities, v.sub.gj, on a dispersion relation for a surface polaritonic mode of the structure for at least one of a corresponding set of prespecified frequencies, .omega..sub.j, and corresponding set of prespecified wavevectors, where j=1 to N.

Low-Cost Oil Quality Sensor Based on Changes in Complex Permittivity

PubMed Central

Pérez, Angel Torres; Hadfield, Mark

2011-01-01

Real time oil quality monitoring techniques help to protect important industry assets, minimize downtime and reduce maintenance costs. The measurement of a lubricant’s complex permittivity is an effective indicator of the oil degradation process and it can be useful in condition based maintenance (CBM) to select the most adequate oil replacement maintenance schedules. A discussion of the working principles of an oil quality sensor based on a marginal oscillator to monitor the losses of the dielectric at high frequencies (>1 MHz) is presented. An electronic design procedure is covered which results in a low cost, effective and ruggedized sensor implementation suitable for use in harsh environments. PMID:22346666

Compensated Arrhenius formalism applied to a conductivity study in poly(propylene glycol) diacrylate monomers.

PubMed

Dubois, F; Derouiche, Y; Leblond, J M; Maschke, U; Douali, R

2015-09-01

The temperature dependence of the ionic conductivity is studied in a series of poly(propylene glycol) diacrylate monomers. The experimental data are analyzed by means of the approach recently proposed by Petrowsky et al. [J. Phys. Chem. B. 113, 5996 (2009)10.1021/jp810095g]. This so-called compensated Arrhenius formalism (CAF) approach takes into account the influence of the dielectric permittivity on the exponential prefactor in the classical Arrhenius equation. The experimental data presented in this paper show a good agreement with the CAF; this means that the exponential prefactor is principally dielectric permittivity dependent. The compensated data revealed two conduction processes with different activation energies; they correspond to low and high temperature ranges, respectively.

Compensated Arrhenius formalism applied to a conductivity study in poly(propylene glycol) diacrylate monomers

NASA Astrophysics Data System (ADS)

Dubois, F.; Derouiche, Y.; Leblond, J. M.; Maschke, U.; Douali, R.

2015-09-01

The temperature dependence of the ionic conductivity is studied in a series of poly(propylene glycol) diacrylate monomers. The experimental data are analyzed by means of the approach recently proposed by Petrowsky et al. [J. Phys. Chem. B. 113, 5996 (2009), 10.1021/jp810095g]. This so-called compensated Arrhenius formalism (CAF) approach takes into account the influence of the dielectric permittivity on the exponential prefactor in the classical Arrhenius equation. The experimental data presented in this paper show a good agreement with the CAF; this means that the exponential prefactor is principally dielectric permittivity dependent. The compensated data revealed two conduction processes with different activation energies; they correspond to low and high temperature ranges, respectively.

Reconstructing the Surface Permittivity Distribution from Data Measured by the CONSERT Instrument aboard Rosetta: Method and Simulations

NASA Astrophysics Data System (ADS)

Plettemeier, D.; Statz, C.; Hegler, S.; Herique, A.; Kofman, W. W.

2014-12-01

One of the main scientific objectives of the Comet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT) aboard Rosetta is to perform a dielectric characterization of comet 67P/Chuyurmov-Gerasimenko's nucleus by means of a bi-static sounding between the lander Philae launched onto the comet's surface and the orbiter Rosetta. For the sounding, the lander part of CONSERT will receive and process the radio signal emitted by the orbiter part of the instrument and transmit a signal to the orbiter to be received by CONSERT. CONSERT will also be operated as bi-static RADAR during the descent of the lander Philae onto the comet's surface. From data measured during the descent, we aim at reconstructing a surface permittivity map of the comet at the landing site and along the path below the descent trajectory. This surface permittivity map will give information on the bulk material right below and around the landing site and the surface roughness in areas covered by the instrument along the descent. The proposed method to estimate the surface permittivity distribution is based on a least-squares based inversion approach in frequency domain. The direct problem of simulating the wave-propagation between lander and orbiter at line-of-sight and the signal reflected on the comet's surface is modelled using a dielectric physical optics approximation. Restrictions on the measurement positions by the descent orbitography and limitations on the instrument dynamic range will be dealt with by application of a regularization technique where the surface permittivity distribution and the gradient with regard to the permittivity is projected in a domain defined by a viable model of the spatial material and roughness distribution. The least-squares optimization step of the reconstruction is performed in such domain on a reduced set of parameters yielding stable results. The viability of the proposed method is demonstrated by reconstruction results based on simulated data.

Tailoring dielectric resonator geometries for directional scattering and Huygens’ metasurfaces

DOE PAGES

Campione, Salvatore; Basilio, Lorena I.; Warne, Larry K.; ...

2015-01-28

In this paper we describe a methodology for tailoring the design of metamaterial dielectric resonators, which represent a promising path toward low-loss metamaterials at optical frequencies. We first describe a procedure to decompose the far field scattered by subwavelength resonators in terms of multipolar field components, providing explicit expressions for the multipolar far fields. We apply this formulation to confirm that an isolated high-permittivity dielectric cube resonator possesses frequency separated electric and magnetic dipole resonances, as well as a magnetic quadrupole resonance in close proximity to the electric dipole resonance. We then introduce multiple dielectric gaps to the resonator geometrymore » in a manner suggested by perturbation theory, and demonstrate the ability to overlap the electric and magnetic dipole resonances, thereby enabling directional scattering by satisfying the first Kerker condition. We further demonstrate the ability to push the quadrupole resonance away from the degenerate dipole resonances to achieve local behavior. These properties are confirmed through the multipolar expansion and show that the use of geometries suggested by perturbation theory is a viable route to achieve purely dipole resonances for metamaterial applications such as wave-front manipulation with Huygens’ metasurfaces. Our results are fully scalable across any frequency bands where high-permittivity dielectric materials are available, including microwave, THz, and infrared frequencies.« less

Electrical Characterization of Glycerin: Water Mixtures: Implications for Use as a Coupling Medium in Microwave Tomography

PubMed Central

Meaney, Paul M.; Fox, Colleen J.; Geimer, Shireen D.; Paulsen, Keith D.

2016-01-01

We examine the broadband behavior of complex electrical properties of glycerin and water mixtures over the frequency range of 0.1 – 25.0 GHz, especially as they relate to using these liquids as coupling media for microwave tomographic imaging. Their combination is unique in that they are mutually miscible over the full range of concentrations which allows them to be tailored to dielectric property matching for biological tissues. While the resultant mixture properties are partially driven by differences in the inherent low frequency permittivity of each constituent, relaxation frequency shifts play a disproportionately larger role in increasing the permittivity dispersion while also dramatically increasing the effective conductivity over the frequency range of 1 to 3 GHz. For the full range of mixture ratios, the relaxation frequency shifts from 17.5 GHz for 0% glycerin to less than 0.1 GHz for 100% glycerin. Of particular interest is the fact that the conductivity stays above 1.0 S/m over the 1–3 GHz range for glycerin mixture ratios (70–90% glycerin) we use for microwave breast tomography. The high level of attenuation is critical for suppressing unwanted multipath signals. This paper presents a full characterization of these liquids along with a discussion of their benefits and limitations in the context of microwave tomography. PMID:28507391

Temperature dependent x-ray diffraction and dielectric studies of multiferroic GaFeO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Rajeev; Mall, Ashish Kumar, E-mail: ashishm@iitk.ac.in; Gupta, Rajeev

2016-05-06

Polycrystalline GaFeO{sub 3} (GFO) samples were synthesized by sol-gel method. The structural and dielectric properties of GaFeO{sub 3} ceramic have been investigated by a combination of XRD and permittivity measurement. The X-ray diffraction spectra shows single phase orthorhombically distorted perovskite structure with Pc2{sub 1}n symmetry over a wide range of temperature 300 K to 600 K, with no evidence of any phase transition. Refined lattice parameters (a, b, c and V) increases with increasing temperature. Temperature dependent dielectric properties were investigated in the frequency range from 100Hz–5MHz. Impedance spectroscopy study on the sample showed that the dielectric constant and acmore » conductivity with frequency increases on increasing the temperature. Cole-Cole plots suggest that the response from grain is dominant at low temperature whereas grain boundary response overcomes as temperature increases. The relaxation activation energy (calculated from Cole-Cole plots) value is found to be 0.32 eV for the grain boundary. We believe that the oxygen ion vacancies play an important role in conduction processes at higher temperatures.« less

Loss/gain-induced ultrathin antireflection coatings

PubMed Central

Luo, Jie; Li, Sucheng; Hou, Bo; Lai, Yun

2016-01-01

Tradional antireflection coatings composed of dielectric layers usually require the thickness to be larger than quarter wavelength. Here, we demonstrate that materials with permittivity or permeability dominated by imaginary parts, i.e. lossy or gain media, can realize non-resonant antireflection coatings in deep sub-wavelength scale. Interestingly, while the reflected waves are eliminated as in traditional dielectric antireflection coatings, the transmitted waves can be enhanced or reduced, depending on whether gain or lossy media are applied, respectively. We provide a unified theory for the design of such ultrathin antireflection coatings, showing that under different polarizations and incident angles, different types of ultrathin coatings should be applied. Especially, under transverse magnetic polarization, the requirement shows a switch between gain and lossy media at Brewster angle. As a proof of principle, by using conductive films as a special type of lossy antireflection coatings, we experimentally demonstrate the suppression of Fabry-Pérot resonances in a broad frequency range for microwaves. This valuable functionality can be applied to remove undesired resonant effects, such as the frequency-dependent side lobes induced by resonances in dielectric coverings of antennas. Our work provides a guide for the design of ultrathin antireflection coatings as well as their applications in broadband reflectionless devices. PMID:27349750

Effect of NiO substitution on the structural and dielectric behaviour of NaNbO3

NASA Astrophysics Data System (ADS)

George, R. T.; Joshi, D. C.; Nayak, S.; Tiwari, N.; Chauhan, R. N.; Pramanik, P.; Dar, T. A.; Ghosh, S.; Thota, S.

2018-02-01

The structural and dielectric properties of NiO substituted NaNbO3 ceramics are reported. The orthorhombic (Pmna) crystal structure of NaNbO3 transforms to a lower symmetry monoclinic phase (Pbma) after the dilute dispersion of NiO. X-ray photoelectron spectroscopy reveals pentavalent "Nb," monovalent "Na," and divalent "Ni" states along with the signatures of non-local screening effects. The antiferroelectric to paraelectric transition (TAFE) accompanied by a structural change from the orthorhombic to the tetragonal phase shifts by 55 °C toward the low-temperature side, whereas the morphotropic phase boundary (TO-M) moves toward a higher temperature by 28 °C for nominal substitutions ( x ≤0.10 ). The generalized Lyddane-Sachs-Teller expression (ε0/-S'ε∞)= (ωl/ωt ) 2 and thermodynamic free energy models are employed to explain the anomalous behaviour of the temperature dependence of relative dielectric permittivity ( εr (T)) across TAFE and TO-M. The frequency dependence of ac-conductivity σac(ω) follows the Jonscher power law (σac = σ(0) + Aωs), suggesting the dominance of the phonon-assisted hopping mechanism, whereas the frequency independent term (σ(0)) was explained by Funke's Jump-Relaxation Model.

Titanium dioxide thin films deposited by pulsed laser deposition and integration in radio frequency devices: Study of structure, optical and dielectric properties

NASA Astrophysics Data System (ADS)

Orlianges, Jean-Christophe; Crunteanu, Aurelian; Pothier, Arnaud; Merle-Mejean, Therese; Blondy, Pierre; Champeaux, Corinne

2012-12-01

Titanium dioxide presents a wide range of technological application possibilities due to its dielectric, electrochemical, photocatalytic and optical properties. The three TiO2 allotropic forms: anatase, rutile and brookite are also interesting, since they exhibit different properties, stabilities and growth modes. For instance, rutile has a high dielectric permittivity, of particular interest for the integration as dielectric in components such as microelectromechanical systems (MEMS) for radio frequency (RF) devices. In this study, titanium dioxide thin films are deposited by pulsed laser deposition. Characterizations by Raman spectroscopy and X-ray diffraction show the evolution of the structural properties. Thin films optical properties are investigated using spectroscopic ellipsometry and transmission measurements from UV to IR range. Co-planar waveguide (CPW) devices are fabricated based on these films. Their performances are measured in the RF domain and compared to simulation, leading to relative permittivity values in the range 30-120, showing the potentialities of the deposited material for capacitive switches applications.

An ultra-wideband wire spiral antenna for in-body communications using different material matching layers.

PubMed

Khaleghi, Ali; Balasingham, Ilangko; Chavez-Santiago, Raul

2014-01-01

In this work an ultra-wideband wire antenna was designed and fabricated for transmitting/receiving signals to/from inside the human body. The antenna provides high gain and thus high field intensity in its broadside direction; hence, a high energy density wireless can be established with the inner body. The proposed antenna operates in the frequency band of 3-10 GHz with an impedance of 200 Ohms in free space. The antenna was embedded in different materials with permittivity values ranging from 12 to 74 in order to evaluate the matching layer effect on wave propagation from outside to inside the body. The antenna port impedance was adjusted by using matching circuits. The electric field intensity inside the human chest was calculated for different materials and depths. The best improvement in wave penetration was obtained for the frequency band of 750-1000 MHz by embedding the antenna inside a material with permittivity equal to 27.

Optical properties of single infrared resonant circular microcavities for surface phonon polaritons.

PubMed

Wang, Tao; Li, Peining; Hauer, Benedikt; Chigrin, Dmitry N; Taubner, Thomas

2013-11-13

Plasmonic antennas are crucial components for nano-optics and have been extensively used to enhance sensing, spectroscopy, light emission, photodetection, and others. Recently, there is a trend to search for new plasmonic materials with low intrinsic loss at new plasmon frequencies. As an alternative to metals, polar crystals have a negative real part of permittivity in the Reststrahlen band and support surface phonon polaritons (SPhPs) with weak damping. Here, we experimentally demonstrate the resonance of single circular microcavities in a thin gold film deposited on a silicon carbide (SiC) substrate in the mid-infrared range. Specifically, the negative permittivity of SiC leads to a well-defined, size-tunable SPhP resonance with a Q factor of around 60 which is much higher than those in surface plasmon polariton (SPP) resonators with similar structures. These infrared resonant microcavities provide new possibilities for widespread applications such as enhanced spectroscopy, sensing, coherent thermal emission, and infrared photodetectors among others throughout the infrared frequency range.

Microwave and millimeter wave dielectric permittivity and magnetic permeability of epsilon-gallium-iron-oxide nano-powders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chao, Liu, E-mail: liu.chao@tufts.edu; Afsar, Mohammed N.; Ohkoshi, Shin-ichi

2015-05-07

In millimeter wave frequency range, hexagonal ferrites with high uniaxial anisotropic magnetic fields are used as absorbers. These ferrites include M-type barium ferrite (BaFe{sub 12}O{sub 19}) and strontium ferrite (SrFe{sub 12}O{sub 19}), which have natural ferromagnetic resonant frequency range from 40 GHz to 60 GHz. However, the higher frequency range lacks suitable materials that support the higher frequency ferromagnetic resonance. A series of gallium-substituted ε-iron oxides (ε-Ga{sub x}Fe{sub 2−x}O{sub 3}) are synthesized, which have ferromagnetic resonant frequencies appearing over the frequency range of 30 GHz to 150 GHz. The ε-Ga{sub x}Fe{sub 2−x}O{sub 3} is synthesized by the sol-gel method. The particlemore » sizes are observed to be smaller than 100 nm. In this paper, in-waveguide transmission and reflection method and the free space magneto-optical approach have been employed to study these newly developed ε-Ga{sub x}Fe{sub 2−x}O{sub 3} particles in millimeter waves. These techniques enable to obtain precise transmission spectra to determine the dielectric and magnetic properties of both isotropic and anisotropic ferrites in the microwave and millimeter wave frequency range from single set of direct measurements. The complex dielectric permittivity and magnetic permeability spectra of ε-Ga{sub x}Fe{sub 2−x}O{sub 3} are shown in this paper. Strong ferromagnetic resonances at different frequencies determined by the x parameter are found.« less

Mid-infrared metamaterial based on perforated SiC membrane: engineering optical response using surface phonon polaritons

NASA Astrophysics Data System (ADS)

Korobkin, D.; Urzhumov, Y. A.; Neuner, B., III; Zorman, C.; Zhang, Z.; Mayergoyz, I. D.; Shvets, G.

2007-09-01

We theoretically and experimentally study electromagnetic properties of a novel mid-infrared metamaterial: optically thin silicon carbide (SiC) membrane perforated by an array of sub-wavelength holes. Giant absorption and transmission is found using Fourier transformed infrared (FTIR) microscopy and explained by introducing a frequency-dependent effective permittivity ɛeff(ω) of the perforated film. The value of ɛeff(ω) is determined by the excitation of two distinct types of hole resonances: delocalized slow surface polaritons (SSPs) whose frequencies are largely determined by the array period, and a localized surface polariton (LSP) corresponding to the resonance of an isolated hole. Only SSPs are shown to modify ɛeff(ω) strongly enough to cause giant transmission and absorption. Because of the sub-wavelength period of the hole array, anomalous optical properties can be directly traced to surface polaritons, and their interpretation is not obscured by diffractive effects. Giant absorbance of this metamaterial can be utilized in designing highly efficient thermal radiation sources.

Dielectric and structural properties of diffuse ferroelectric phase transition in Pb1.85K1.15Li0.15Nb5O15 ceramic

NASA Astrophysics Data System (ADS)

Choukri, E.; Gagou, Y.; Mezzane, D.; Abkhar, Z.; El Moznine, R.; Luk'yanchuk, I.; Saint-Grégoire, P.; Kavokin, A. V.

2011-02-01

We studied the structural and dielectric properties of new Tetragonal Tungsten Bronze (TTB) ceramics Pb1.85K1.15Li0.15Nb5O15 that was synthesized by solid-state reaction. We pay a special attention to the diffuse phase transition (DPT) that occurs close to 425 °C. Using dielectric measurements in a frequency range of 10 Hz-1 MHz and in the temperature range 30-560 °C, we have shown that the real permittivity close to DPT is well described by Santos-Eiras phenomenological model. Space-charge polarization, relaxation phenomena and free charges conductivity have been analyzed using dielectric spectroscopy impedance and modulus characterization. Cole-Cole plots show a non-Debye (polydispersive) type relaxation. In paraelectric phase the Arrhenius activation energy was determined as Eτ = 0.72 eV. We demonstrated that frequency dependence of ac conductivity at different temperatures obeys the Jonscher's universal law: σac = σdc + A(ω)n.

An instrument for measuring the complex permittivity of the Martian top soil

NASA Technical Reports Server (NTRS)

Grard, R.

1988-01-01

This permittivity measuring instrument measures the resistivity rho and the relative dielectric constant epsilon sub r of the Martian top soil along the path of a rover. This aim is achieved by measuring the real and imaginary parts of the complex permittivity epsilon = epsilon sub r - j epsilon sub i where epsilon sub i = omega epsilon sub o rho/1; epsilon sub 1 is the permittivity of vacuum and omega is a variable angular working frequency. The experimental technique consists in evaluating the mutual, or transfer, impedance of a quadrupolar probe, i.e., in quantifying the influence of the Martian ground on the electrical coupling of two Hertz dipoles. The horizontal and vertical spatial resolutions are of the order of the length and separation of the dipoles, typically 1 to 2 metres. The four-electrode method for measuring the ground resistivity on earth was first applied by Wenner and Schlumberger, but the proposed investigation bears closer resemblance to a similar instrument developed for ground surveying at shallow depth, in connection with archaelogical and pedological research. A quadrupolar probe will provide essential information about the electric properties of the Martian ground and will contribute usefully to the identification of the soil structure and composition in association with other experimental equipment (camera, infra-red detector, gamma and X-ray spectrometers, chemical analyzers, ground temperature probes).

Colossal permittivity induced by lattice mirror reflection symmetry breaking in Ba7Ir3O13+x(0 <= x <= 1.5) epitaxial thin films

NASA Astrophysics Data System (ADS)

Miao, Ludi; Xin, Yan; Zhu, Huiwen; Xu, Hong; Luo, Sijun; Talbayev, Diyar; Stanislavchuk, T. N.; Sirenko, A. A.; Mao, Zhiqiang

2014-03-01

Materials with colossal permittivity (CP) at room temperature hold tremendous promise in modern microelectronics as well as high-energy-density storage applications. Despite several proposed mechanisms that lead torecent discoveries of a series of new CP materials such as Nb, In co-doped TiO2 and CaCu3Ti4O12 ceramics, it is imperative to find other approaches which can further guide the search for new CP materials. In this talk, we will demonstrate a new mechanism for CP: the breaking of mirror reflection symmetry of lattice can cause CP. This mechanism was revealed in a new layered iridate Ba7Ir3O13+x (BIO) thin film we recently discovered. Structural characterization of BIO films show that its mirror reflection symmetry is broken along b-axis, but preserved along a- and c-axes. Dielectric property measurements of BIO films at room temperature show a CP (103-10<4) along the in-plane direction, but a much smaller permittivity (10- 20) along the c-axis, in the 102- 106 Hz frequency range. Such unusually large anisotropy in permittivity testifies to the significant role of the structural in-plane mirror reflection symmetry breaking in inducing CP. This work is supported by DOD-ARO under Grant No. W911NF0910530.

Influence of thermal aging on AC leakage current in XLPE insulation

NASA Astrophysics Data System (ADS)

Geng, Pulong; Song, Jiancheng; Tian, Muqin; Lei, Zhipeng; Du, Yakun

2018-02-01

Cross-linked polyethylene (XLPE) has been widely used as cable insulation material because of its excellent dielectric properties, thermal stability and solvent resistance. To understand the influence of thermal aging on AC leakage current in XLPE insulation, all XLPE specimens were aged in oven in temperature range from 120 °C to 150 °C, and a series of tests were conducted on these XLPE specimens in different aging stages to measure the characteristic parameters, such as complex permittivity, leakage current and complex dielectric modulus. In the experiments, the effects of thermal aging, temperature and frequency on the AC leakage current in XLPE insulation were studied by analyzing complex dielectric constant and dielectric relaxation modulus spectrum, the change of relaxation peak and activation energy. It has been found that the active part of leakage current increases sharply with the increase of aging degree, and the test temperature and frequency have an influence on AC leakage current but the influence of test temperature is mainly reflected in the low frequency region. In addition, it has been shown by the experiments that the reactive part of leakage current exhibits a strong frequency dependent characteristic in the testing frequency range from 10-2 Hz to 105 Hz, but the influence of test temperature and thermal aging on it is relatively small.

Small polaronic hole hopping mechanism and Maxwell-Wagner relaxation in NdFeO3

NASA Astrophysics Data System (ADS)

Ahmad, I.; Akhtar, M. J.; Younas, M.; Siddique, M.; Hasan, M. M.

2012-10-01

In the modern micro-electronics, transition metal oxides due to their colossal values of dielectric permittivity possess huge potential for the development of capacitive energy storage devices. In the present work, the dielectric permittivity and the effects of temperature and frequency on the electrical transport properties of polycrystalline NdFeO3, prepared by solid state reaction method, are discussed. Room temperature Mossbauer spectrum confirms the phase purity, octahedral environment for Fe ion, and high spin state of Fe3+ ion. From the impedance spectroscopic measurements, three relaxation processes are observed, which are related to grains, grain boundaries (gbs), and electrode-semiconductor contact in the measured temperature and frequency ranges. Decrease in resistances and relaxation times of the grains and grain boundaries with temperature confirms the involvement of thermally activated conduction mechanisms. Same type of charge carriers (i.e., small polaron hole hopping) have been found responsible for conduction and relaxation processes through the grain and grain boundaries. The huge value of the dielectric constant (˜8 × 103) at high temperature and low frequency is correlated to the Maxwell-Wagner relaxation due to electrode-sample contact.

The presence of two electron beams in a Cherenkov maser and their different behavior for generation and amplification of THz electromagnetic waves

NASA Astrophysics Data System (ADS)

Hajijamali-Arani, Zeinab; Jazi, Bahram

2017-04-01

The wave propagation in a cylindrical metallic waveguide including a dielectric tube is investigated. Two electron beams with opposite velocities are injected in the system as energy sources. It is shown that one of the electron beams is responsible for Cherenkov radiation, the other one is as the stabilizer. The dispersion relation of the waves, impedance of the waves, operating frequency of the system and time growth rate of THz waves are investigated. The effects of relative permittivity constant of dielectric tube, the geometrical dimensions, and the accelerating voltage on time growth rate are investigated. The effective factors on the frequency spectra of the waveguide will be presented too. It is obtained that the time growth rate of the waves increases with increasing the dielectric permittivity and thickness of the dielectric tube. In addition, with increasing the accelerating voltage the time growth rate has opposite behavior in some of the branches of the dispersion graphs. The power obtained in the excitation process for one branch of the dispersion graphs is presented. The graph of variations of transported power with respect to the wave frequency is plotted.

High-Frequency Electromagnetic Impedance Measurements for Characterization, Monitoring and Verification Efforts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Ki Ha; Becker, Alex; Tseng, Hung-Wen

2004-06-16

Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic (EM) measurements at frequencies between 0.1 and 100 MHz are important for such applications, because the induction number of many targets is small and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high-resolution imaging, accurate measurements are necessary so the field data canmore » be mapped into the space of the subsurface parameters. We are developing a non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using the EM impedance approach (Frangos, 2001; Lee and Becker, 2001; Song et al., 2002, Tseng et al., 2003). Electric and magnetic sensors are being tested and calibrated on sea water and in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques.« less

Wheel-Based Ice Sensors for Road Vehicles

NASA Technical Reports Server (NTRS)

Arndt, G. Dickey; Fink, Patrick W.; Ngo, Phong H.; Carl, James R.

2011-01-01

Wheel-based sensors for detection of ice on roads and approximate measurement of the thickness of the ice are under development. These sensors could be used to alert drivers to hazardous local icing conditions in real time. In addition, local ice-thickness measurements by these sensors could serve as guidance for the minimum amount of sand and salt required to be dispensed locally onto road surfaces to ensure safety, thereby helping road crews to utilize their total supplies of sand and salt more efficiently. Like some aircraft wing-surface ice sensors described in a number of previous NASA Tech Briefs articles, the wheelbased ice sensors are based, variously, on measurements of changes in capacitance and/or in radio-frequency impedance as affected by ice on surfaces. In the case of ice on road surfaces, the measurable changes in capacitance and/or impedance are attributable to differences among the electric permittivities of air, ice, water, concrete, and soil. In addition, a related phenomenon that can be useful for distinguishing between ice and water is a specific transition in the permittivity of ice at a temperature- dependent frequency. This feature also provides a continuous calibration of the sensor to allow for changing road conditions. Several configurations of wheel-based ice sensors are under consideration. For example, in a simple two-electrode capacitor configuration, one of the electrodes would be a circumferential electrode within a tire, and the ground would be used as the second electrode. Optionally, the steel belts that are already standard parts of many tires could be used as the circumferential electrodes. In another example (see figure), multiple electrodes would be embedded in rubber between the steel belt and the outer tire surface. These electrodes would be excited in alternating polarities at one or more suitable audio or radio frequencies to provide nearly continuous monitoring of the road surface under the tire. In still another example, one or more microwave stripline(s) or coplanar waveguide(s) would be embedded in a tire near its outer surface; in comparison with lower-frequency capacitive devices, a device of this type could be more sensitive.

Method and Apparatus for Measuring Fluid Flow

NASA Technical Reports Server (NTRS)

Arndt, G. Dickey (Inventor); Nguyen, Than X. (Inventor); Carl, James R. (Inventor)

1995-01-01

The invention is a method and apparatus for monitoring the presence, concentration, and the movement of fluids. It is based on utilizing electromagnetic measurements of the complex permittivity of the fluids for detecting and monitoring the fluid. More particularly the apparatus uses one or more microwave probes which are placed at the locations where the measurements are to be made. A radio frequency signal is transmitted to the probe and the reflected signal is phase and amplitude detected at a rapid rate for the purpose of identifying the fluids, based on their dielectric constant at the probe. The apparatus can be used for multiple purposes including measures of flow rates, turbulence, dispersion, fluid identification, and changes in flow conditions of multiple fluids or multiple states of a single fluid in a flowline or a holding container. The apparatus includes a probe consisting of two electrical conductors separated by an insulator. A radio frequency signal is communicated to the probe and is reflected back from the portion of the probe exposed to the fluid. The radio frequency signal also provides a reference signal. An oscillator generates a second signal which combined with each of the reference signal and the reflected signal to produce signals of lower frequencies to facilitate filtering and amplifying those signals. The two signals are then mixed in a detector to produce an output signal that is representative of the phase and amplitude change caused by the reflection of the signal at the probe exposed to the fluid. The detector may be a dual phase detector that provides two such output signals that are in phase quadrature. A phase shifter may be provided for selectively changing the phase of the reference signal to improve the sensitivity of at least one of the output signals for more accurate readings and/or for calibration purposes. The two outputs that are in quadrature with respect to each other may be simultaneously monitored to account for drift errors. The output signals are digitized and provided to a computer at a sample rate which may be very high. The computer is operable to identify the fluid based on its complex permittivity as may be useful for identifying the flow rates, determining the fluid mixture ratio, detecting impurities in the fluid, and so forth. Novelty is believed to reside in the use of the real part of complex permittivity to measure small difference in permittivity of the fluid.

Structure and colossal dielectric permittivity of Ca2TiCrO6 ceramics

NASA Astrophysics Data System (ADS)

Yan-Qing, Tan; Meng, Yan; Yong-Mei, Hao

2013-01-01

A colossal permittivity ceramic material, Ca2TiCrO6, was successfully synthesized by the conventional solid-state reaction, and was characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), x-ray photoemission spectroscopy (XPS) and x-ray diffraction (XRD). Rietveld refinement of XRD data indicated that the material crystallized in orthorhombic structure with space group pbnm. SEM displayed Ca2TiCrO6 ceramic grains packed uniformly with the size range 5-20 µm. XPS analyses indicated that elemental chromium and titanium of the material were in mixed valence. The corresponding dielectric property was tested in the frequency range 1 kHz-1 MHz and the temperature range 213-453 K, and the ceramics exhibited a relaxation-like dielectric behaviour. Importantly, the permittivity of Ca2TiCrO6 could reach 80 000 at 298 K (100 Hz) and was maintained at 40 000 up to 398 K at 1 MHz, which could be attributed to the ion disorder and mixed valence of Cr3+/Cr6+ and Ti3+/Ti4+.

Microwave and Millimeter Wave Properties of Vertically-Aligned Single Wall Carbon Nanotubes Films

NASA Astrophysics Data System (ADS)

Haddadi, K.; Tripon-Canseliet, C.; Hivin, Q.; Ducournau, G.; Teo, E.; Coquet, P.; Tay, B. K.; Lepilliet, S.; Avramovic, V.; Chazelas, J.; Decoster, D.

2016-05-01

We present the experimental determination of the complex permittivity of vertically aligned single wall carbon nanotubes (SWCNTs) films grown on quartz substrates in the microwave regime from 10 MHz up to 67 GHz, with the electrical field perpendicular to the main axis of the carbon nanotubes (CNTs), based on coplanar waveguide transmission line approach together with the measurement of the microwave impedance of top metalized vertically—aligned SWCNTs grown on conductive silicon substrates up to 26 GHz. From coplanar waveguide measurements, we obtain a real part of the permittivity almost equal to unity, which is interpreted in terms of low carbon atom density (3 × 1019 at/cm3) associated with a very low imaginary part of permittivity (<10-3) in the frequency range considered due to a very small perpendicular conductivity. The microwave impedance of a vertically aligned CNTs bundle equivalent to a low resistance reveals a good conductivity (3 S/cm) parallel to the CNTs axis. From these two kinds of data, we experimentally demonstrate the tensor nature of the vertically grown CNTs bundles.

Permittivity of naphthenic acid-water mixture.

PubMed

Mishra, Sabyasachi; Meda, Venkatesh; Dalai, Ajay

2007-01-01

Naphthenic acid (NA) is predominantly a mono-carboxylic acid obtained as a by-product of petroleum refining with variable composition and ingredients. It is reported that water affected by processes in the petroleum industries generally contains 40-120 mg IL of naphthenic acid which is considered to be in the range of toxicity to human consumption [Clemente et. al, 2005; McMartin, 2003]. This contaminated water needs treatment before its use as drinking water by remote communities. Recent literature suggests that NAs could be separated from diesel fuel using microwave radiation [Lingzhao et. al, 2004]. Removal of naphthenic acid from vacuum cut #1 distillate oil of Daqing using microwaves has also been reported by Huang et. al [2006]. The microwave treatment can be applied to drinking water containing small concentrations of naphthenic acid. In this case permittivity information is useful in designing a microwave applicator and modeling studies. Permittivity measurements were done using a HP 8510 Vector Network Analyzer and coaxial probe reflection method to study the dielectric properties of naphthenic acid in water. The effects of process variables such as frequency, concentration and temperature on dielectric properties were determined.

Effect of Barium Titanate Particles on Dielectric and Electro-Optical Properties of a Smectic-a Liquid Crystal

NASA Astrophysics Data System (ADS)

Ramazanov, M. A.; Imamaliyev, A. R.; Humbatov, Sh. A.; Agamaliev, Z. A.

2018-02-01

The effect of submicron ferroelectric BaTiO3 particles on the dielectric and electro-optical properties of the smectic-A liquid crystal (LC) with a high negative dielectric anisotropy is investigated. It is shown that the addition of BaTiO3 particles with a weight amount of 1% reduces insignificantly the transverse dielectric permittivity component ɛ ⊥ of, but significantly increases the longitudinal dielectric permittivity component ɛ // of the smectic-A LC. As a result, the anisotropy of the dielectric permittivity Δɛ = ɛ // - ɛ ⊥ of the smectic-A LC decreases. The addition of BaTiO3 particles shifts the dispersion ɛ ⊥ toward lower frequencies. Both components of the electrical conductivity of LC colloid + BaTiO3 are an order of magnitude higher than of the pure LC. The threshold voltage of the homeotropic-planar transition of the colloid is twice smaller, and its velocity is 6 times higher in comparison with the pure LC. A simple model explaining qualitatively all results obtained is presented.

Detection of anomalies in radio tomography of asteroids: Source count and forward errors

NASA Astrophysics Data System (ADS)

Pursiainen, S.; Kaasalainen, M.

2014-09-01

The purpose of this study was to advance numerical methods for radio tomography in which asteroid's internal electric permittivity distribution is to be recovered from radio frequency data gathered by an orbiter. The focus was on signal generation via multiple sources (transponders) providing one potential, or even essential, scenario to be implemented in a challenging in situ measurement environment and within tight payload limits. As a novel feature, the effects of forward errors including noise and a priori uncertainty of the forward (data) simulation were examined through a combination of the iterative alternating sequential (IAS) inverse algorithm and finite-difference time-domain (FDTD) simulation of time evolution data. Single and multiple source scenarios were compared in two-dimensional localization of permittivity anomalies. Three different anomaly strengths and four levels of total noise were tested. Results suggest, among other things, that multiple sources can be necessary to obtain appropriate results, for example, to distinguish three separate anomalies with permittivity less or equal than half of the background value, relevant in recovery of internal cavities.

Surface Josephson plasma waves in layered superconductors above the plasma frequency: evidence for a negative index of refraction.

PubMed

Golick, V A; Kadygrob, D V; Yampol'skii, V A; Rakhmanov, A L; Ivanov, B A; Nori, Franco

2010-05-07

We predict a new branch of surface Josephson plasma waves (SJPWs) in layered superconductors for frequencies higher than the Josephson plasma frequency. In this frequency range, the permittivity tensor components along and transverse to the layers have different signs, which is usually associated with negative refraction. However, for these frequencies, the bulk Josephson plasma waves cannot be matched with the incident and reflected waves in the vacuum, and, instead of the negative-refractive properties, abnormal surface modes appear within the frequency band expected for bulk modes. We also discuss the excitation of high-frequency SJPWs by means of the attenuated-total-reflection method.

Graphene and temperature controlled butterfly shape in permittivity-field loops of ferroelectric polymer nanocomposites

NASA Astrophysics Data System (ADS)

Adohi, B. J. P.; Brosseau, C.; Laur, V.; Haidar, B.

2017-01-01

We report on the field-dependent polarization of graphene (GE) filled poly[vinylidene fluoride-co-trifluoroethylene] P(VDF-TrFE) nanostructures fabricated by mechanical melt mixing. This study shows an increase in effective permittivity of these nanomaterials on increasing the GE loading in a manner that is consistent with standard mixing law. Detailed characterization of the unsaturated ferroelectric hysteresis, as well as the butterfly shape of the effective permittivity versus electric bias, of the samples are presented. For GE content set to 9.1 wt. % in the samples containing 50/50 wt. % (VDF/TrFE), the maximum polarization increases by 260% with respect to that of the neat polymer matrix. With a higher VDF content, 73 wt. %, the coercive field remains constant over the range of GE content explored. Additionally, our results highlight the strong impact of the GE loading and temperature on the butterfly shape in permittivity-field loops of these nanocomposites. The experimental findings are consistent with theoretical predictions of the modified Johnson's model [Narayanan et al., Appl. Phys. Lett. 100, 022907 (2012)]. Our findings can open avenues for interplay between conductive nanofillers and ferroelectricity in soft nanomaterials with controlled phase transitions.

Measurement of the Dielectric Constant of Seawater at L-Band: Techniques and Measurements

NASA Technical Reports Server (NTRS)

Lang, R.; Utku, C.; Tarkocin, Y.; LeVine, D.

2009-01-01

Satellite instruments, that will monitor salinity from space in the near future, require an accurate relationship between salinity/temperature and seawater dielectric constant. This paper will review measurements that were made of the dielectric constant of seawater during the past several years. The objective of the measurements is to determine the dependence of the dielectric constant of seawater on salinity and on temperature, more accurately than in the past. by taking advantage of modem instrumentation. The measurements of seawater permittivity have been performed as a function of salinity and temperature using a transmission resonant cavity technique. The measurements have been made in the salinity range of 10 to 38 psu and in the temperature range of IOU C to 35 C. These results will be useful in algorithm development for sensor systems such as SMOS and Aquarius. The measurement system consists of a brass microwave cavity that is resonant at 1.413 GHz. The seawater is introduced into the cavity through a capillary glass tube having an inner diameter of 0.1 mm. The diameter of the tube has been made very small so that the amount of seawater introduced in the cavity is small - thus maintaining the sensitivity of the measurements and allowing the use of perturbation theory predicting the seawater permittivity. The change in resonant frequency and the change in cavity Q can be used to determine the real and imaginary pare of the dielectric constant of seawater introduced into the slender tube. The microwave measurements are made by an HPS722D network analyzer. The cavity has been immersed in a uateriethylene-glycol bath which is connected to a Lauda circulator. The circulator keeps the brass cavity at a temperature constant to within 0.01 degrees. The system is automated using a Visual Basic program to control the analyzer and to collect the data. The results of the dielectric constant measurements of seawater will be presented. The measurement results will be compared with permittivity values generated from the Kline and Swift relationship. Two methods of calibration will be discussed, The errors that each technique introduces into the measurement resulls will be reviewed. Temperature stability, frequency drift and the effect of increasing cavity transmission loss on the unloaded cavity Q will also be discussed.

On the dielectric dispersion and absorption in nanosized manganese zinc mixed ferrites.

PubMed

Veena Gopalan, E; Malini, K A; Sakthi Kumar, D; Yoshida, Yasuhiko; Al-Omari, I A; Saravanan, S; Anantharaman, M R

2009-04-08

The temperature and frequency dependence of dielectric permittivity and dielectric loss of nanosized Mn(1-x)Zn(x)Fe(2)O(4) (for x = 0, 0.2, 0.4, 0.6, 0.8, 1) were investigated. The impact of zinc substitution on the dielectric properties of the mixed ferrite is elucidated. Strong dielectric dispersion and broad relaxation were exhibited by Mn(1-x)Zn(x)Fe(2)O(4). The variation of dielectric relaxation time with temperature suggests the involvement of multiple relaxation processes. Cole-Cole plots were employed as an effective tool for studying the observed phenomenon. The activation energies were calculated from relaxation peaks and Cole-Cole plots and found to be consistent with each other and indicative of a polaron conduction.

Angular distribution of hybridization in sputtered carbon thin film

NASA Astrophysics Data System (ADS)

Liu, Y.; Wang, H.; Wei, Z. C.

2017-08-01

The sp3/sp2 ratio of sputtered carbon thin film depends on the ion bombardment process and tailors the physical properties of carbon thin film. In present work, we report the angular distribution of hybridization in magnetron sputtered carbon thin film for the first time. By x-ray photoelectron spectra analyses, it is found that the sp3/sp2 ratio increases linearly with increasing the deposition angle from 0 to 90 degree, which could be attributed to the enhancement of direct knocking-out of near-surface target atoms. In addition, we also derive the sp3/sp2 ratio by simulation on complex permittivity in terahertz frequency using a modified percolation approximation tunneling model. Those derived data consist with the results from x-ray photoelectron spectroscopy.

An estimation of the electrical characteristics of planetary shallow subsurfaces with TAPIR antennas

NASA Astrophysics Data System (ADS)

Le Gall, A.; Reineix, A.; Ciarletti, V.; Berthelier, J. J.; Ney, R.; Dolon, F.; Corbel, C.

2006-06-01

In the frame of the NETLANDER program, we have developed the Terrestrial And Planetary Investigation by Radar (TAPIR) imaging ground-penetrating radar to explore the Martian subsurface at kilometric depths and search for potential water reservoirs. This instrument which is to operate from a fixed lander is based on a new concept which allows one to image the various underground reflectors by determining the direction of propagation of the reflected waves. The electrical parameters of the shallow subsurface (permittivity and conductivity) need to be known to correctly determine the propagation vector. In addition, these electrical parameters can bring valuable information on the nature of the materials close to the surface. The electric antennas of the radar are 35 m long resistively loaded monopoles that are laid on the ground. Their impedance, measured during a dedicated mode of operation of the radar, depends on the electrical parameters of soil and is used to infer the permittivity and conductivity of the upper layer of the subsurface. This paper presents an experimental and theoretical study of the antenna impedance and shows that the frequency profile of the antenna complex impedance can be used to retrieve the geoelectrical characteristics of the soil. Comparisons between a numerical modeling and in situ measurements have been successfully carried over various soils, showing a very good agreement.

Microwave dielectric relaxation spectroscopy study of propylene glycol/ethanol binary mixtures: Temperature dependence

NASA Astrophysics Data System (ADS)

Vishwam, T.; Shihab, Suriya; Murthy, V. R. K.; Tiong, Ha Sie; Sreehari Sastry, S.

2017-05-01

Complex dielectric permittivity measurements of propylene glycol (PG) in ethanol at various mole fractions were measured by using open-ended coaxial probe technique at different temperatures in the frequency range 0.02 < ν/GHz < 20. The dipole moment (μ), excess dipole moment (Δμ),excess permittivity (εE), excess inverse relaxation time(1/τ)E, Bruggeman parameter (fB), excess Helmholtz energy (ΔFE) are determined using experimental data. From the minimum energy based geometry optimization, dipole moments of individual monomers of propylene glycol and ethanol and their binary system have been evaluated theoretically at gaseous state as well as alcoholic medium by using PCM and IEFPCM solvation models from the Hatree-Fock (HF) and Density Functional Theory (DFT-B3LYP) methods with 6-311G* and 6-311G** basis sets. The obtained results have been interpreted in terms of the short and long range ordering of the dipoles, Kirkwood correlation factor (geff), thermodynamic parameters, mean molecular polarizability (αM) and interaction in the mixture through hydrogen bonding. Dielectric relaxation study of propylene glycol in ethanol medium Determination of excess dielectric and thermodynamic parameters Comparison of experimental dipole moment with theoretical calculations Interpretation of the molecular interactions in the liquid through H-bonding Correlation between the evaluated dielectric parameters and theoretical results

Ultrafast re-structuring of the electronic landscape of transparent dielectrics: new material states (Die-Met)

NASA Astrophysics Data System (ADS)

Gamaly, E. G.; Rode, A. V.

2018-03-01

Swift excitation of transparent dielectrics by ultrashort and highly intense laser pulse leads to ultra-fast re-structuring of the electronic landscape and generates many transient material states, which are continuously reshaped in accord with the changing pulse intensity. These unconventional transient material states, which exhibit simultaneously both dielectric and metallic properties, we termed here as the `Die-Met' states. The excited material is transparent and conductive at the same time. The real part of permittivity of the excited material changes from positive to negative values with the increase of excitation, which affects strongly the interaction process during the laser pulse. When the incident field has a component along the permittivity gradient, the amplitude of the field increases resonantly near the point of zero permittivity, which dramatically changes the interaction mode and increases absorption in a way that is similar to the resonant absorption in plasma. The complex 3D structure of the permittivity makes a transparent part of the excited dielectric (at ɛ 0 > ɛ re > 0) optically active. The electro-magnetic wave gets a twisted trajectory and accrues the geometric phase while passing through such a medium. Both the phase and the rotation of the polarisation plane depend on the 3D permittivity structure. Measuring the transmission, polarisation and the phase of the probe beam allows one to quantitatively identify these new transient states. We discuss the revelations of this effect in different experimental situations and their possible applications.

Realizing thin electromagnetic absorbers for wide incidence angles from commercially available planar circuit materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glover, Brian B; Whites, Kieth W; Radway, Matthew J

2009-01-01

In this study, recent work on engineering R-card surface resistivity with printed metallic patterns is extended to the design of thin electromagnetic absorbers. Thin electromagnetic absorbers for wide incidence angles and both polarizations have recently been computationally verified by Luukkonen et al.. These absorbers are analytically modeled high-impedance surfaces with capacitive arrays of square patches implemented with relatively high dielectric constant and high loss substrate. However, the advantages provided by the accurate analytical model are largely negated by the need to obtain high dielectric constant material with accurately engineered loss. Fig. I(c) illustrates full-wave computational results for an absorber withoutmore » vias engineered as proposed by Luukkonen et al.. Unique values for the dielectric loss are required for different center frequencies. Parameters for the capacitive grid are D=5.0 mm and w=O.l mm for a center frequency of 3.36 GHz. The relative permittivity and thickness is 9.20(1-j0.234) and 1=3.048 mm. Consider a center frequency of5.81 GHz and again 1=3.048 mm, the required parameters for the capacitive grid are D=2.0 mm and w=0.2 mm where the required relative permittivity is now 9.20(1-j0.371) Admittedly, engineered dielectrics are themselves a historically interesting and fruitful research area which benefits today from advances in monolithic fabrication using direct-write of dielectrics with nanometer scale inclusions. However, our objective in the present study is to realize the advantages of the absorber proposed by Luukkonen et al. without resort to engineered lossy dielectrics. Specifically we are restricted to commercially available planer circuit materials without use of in-house direct-write technology or materials engineering capability. The materials considered here are TMM 10 laminate with (35 {mu}lm copper cladding with a complex permittivity 9.20-j0.0022) and Ohmegaply resistor conductor material (maximum 250 {Omega}/sq.). A thin electromagnetic absorber for incidence angles greater than 30deg. but less than 60deg. and both polarizations is computationally demonstrated. This absorber utilizes high-permittivity, low-loss microwave substrate in conjunction with an engineered lossy sheet impedance. The lossy sheet impedance is easily engineered with simple analytical approximations and can be manufactured from commercially available laminate materials on microwave substrate.« less

Dielectric Properties of PMMA and its Composites with ZrO2

NASA Astrophysics Data System (ADS)

Sannakki, Basavaraja; Anita

The polymer films of PMMA with different thickness and its composites with ZrO2 at various weight percentages but of same thickness have been studied. The determination of its dielectric properties, dielectric loss, a.conductivity and dielectric modulus were carried out using capacitance measurements of the above samples as a function of frequency, over the range 50 Hz - 5 MHz at room temperature. The films of PMMA and its composites have been characterized using X-Ray Diffractometer. The dielectric permittivity of films of PMMA behaves nonlinearly as frequency increases over the range 50-300 Hz, where as above 300 Hz the values of dielectric constant remains constant. But it is observed that the dielectric constant of PMMA increases as thickness of the film increases. In case of composite films of PMMA with ZrO2 the values of dielectric permittivity decreases gradually up to frequency of around 1 KHz and at higher frequencies it remains constant for all the weight percentages of ZrO2. The complex form of dielectric modulus of PMMA is obtained from the experimentally measured data of dielectric constant and dielectric loss values. The relaxation time of the orientation of dipoles is obtained from the peak value of angular frequency through the plots of imaginary part of electrical modulus as function of frequency. The impedance of PMMA polymer increases as thickness of the films increases. The a c conductivity of PMMA film remains constant up to frequency of 1 MHz and above. It shows a nonlinear phenomenon with peak values at frequency 4 MHz. Shape and size of the nanoparticles of composite film of PMMA with ZrO2 was analyzed by Field Emission Scanning Electron Microscope (FESEM).

Temperature-Dependent Dielectric Properties of Al/Epoxy Nanocomposites

NASA Astrophysics Data System (ADS)

Wang, Zijun; Zhou, Wenying; Sui, Xuezhen; Dong, Lina; Cai, Huiwu; Zuo, Jing; Chen, Qingguo

2016-06-01

Broadband dielectric spectroscopy was carried out to study the transition in electrical properties of Al/epoxy nanocomposites over the frequency range of 1-107 Hz and the temperature range of -20°C to 200°C. The dielectric permittivity, dissipation factor, and electrical conductivity of the nanocomposites increased with temperature and showed an abrupt increase around the glass transition temperature ( T g). The results clearly reveal an interesting transition of the electrical properties with increasing temperature: insulator below 70°C, conductor at about 70°C. The behavior of the transition in electrical properties of the nanocomposites was explored at different temperatures. The presence of relaxation peaks in the loss tangent and electric modulus spectra of the nanocomposites confirms that the chain segmental dynamics of the polymer is accompanied by the absorption of energy given to the system. It is suggested that the temperature-dependent transition of the electric properties in the nanocomposite is closely associated with the α-relaxation. The large increase in the dissipation factor and electric conductivity depends on the direct current conduction of thermally activated charge carriers resulting from the epoxy matrix above T g.

Response to ``Comment on `Slow Debye-type peak observed in the dielectric response of polyalcohols' '' [J. Chem. Phys. 134, 037101 (2011)

NASA Astrophysics Data System (ADS)

Bergman, R.; Jansson, H.; Swenson, J.

2011-01-01

In our recent article [R. Bergman et al., J. Chem. Phys. 132, 044504 (2010)] we investigated some polyalcohols, i.e., glycerol, xylitol, and sorbitol by dielectric spectroscopy. In the study, a low-frequency peak of Debye character that normally is hidden by the large low-frequency dispersion due to conductivity was revealed by analyzing the real part of the permittivity and by using a thin Teflon film to suppress the low-frequency dispersion. We agree with the comment by Paluch et al. [J. Chem. Phys. 134, 037101 (2011)] that the Teflon film setup will indeed create a peak due to the dc conductivity. However, due to the fact that the location of the peak was almost identical in measurement with and without Teflon, we unfortunately mainly showed the data measured with Teflon, despite that it could also be observed in the real part of the permittivity without using the Teflon setup, as shown in our original article [R. Bergman et al., J. Chem. Phys. 132, 044504 (2010)]. Here, we show that the low-frequency peak of Debye character can also be observed by subtracting the dc conductivity. Furthermore, we show that the modulus representation used in Paluch et al. [J. Chem. Phys. 134, 037101 (2011).] is also not suitable for detecting processes hidden by the conductivity.

Compound surface-plasmon-polariton waves guided by a thin metal layer sandwiched between a homogeneous isotropic dielectric material and a structurally chiral material

NASA Astrophysics Data System (ADS)

Chiadini, Francesco; Fiumara, Vincenzo; Scaglione, Antonio; Lakhtakia, Akhlesh

2016-03-01

Multiple compound surface plasmon-polariton (SPP) waves can be guided by a structure consisting of a sufficiently thick layer of metal sandwiched between a homogeneous isotropic dielectric (HID) material and a dielectric structurally chiral material (SCM). The compound SPP waves are strongly bound to both metal/dielectric interfaces when the thickness of the metal layer is comparable to the skin depth but just to one of the two interfaces when the thickness is much larger. The compound SPP waves differ in phase speed, attenuation rate, and field profile, even though all are excitable at the same frequency. Some compound SPP waves are not greatly affected by the choice of the direction of propagation in the transverse plane but others are, depending on metal thickness. For fixed metal thickness, the number of compound SPP waves depends on the relative permittivity of the HID material, which can be useful for sensing applications.

Conduction mechanism, impedance spectroscopic investigation and dielectric behavior of La0.5Ca0.5-xAgxMnO3 manganites with compositions below the concentration limit of silver solubility in perovskites (0 ≤ x ≤ 0.2).

PubMed

Rahmouni, H; Smari, M; Cherif, B; Dhahri, E; Khirouni, K

2015-06-14

This study presents the electrical properties, complex impedance analysis and dielectrical behavior of La0.5Ca0.5-xAgxMnO3 manganites with compositions below the concentration limit of silver solubility in perovskites (0 ≤ x ≤ 0.2). Transport measurements indicate that all the samples have a semiconductor-like behavior. The metal-semiconductor transition is not observed across the whole temperature range explored [80 K-700 K]. At a specific temperature, a saturation region was marked in the σ (T) curves. We obtained a maximum σdc value at ambient temperature with the introduction of 20% Ag content. Two hopping models were applied to study the conduction mechanism. We found that activation energy (Ea) related to ac-conductivity is lower than the Ea implicated in dc-conductivity. Complex impedance analysis confirms the contribution of grain boundary to conductivity and permits the attribution of grain boundary capacitance evolution to the temperature dependence of the barrier layer width. From the temperature dependence of the average normalized change (ANC), we deduce the temperature at which the available density of trapped charge states vanishes. Such a temperature is close to the temperature at which the saturation region appears in σ(T) curves. Moreover, complex impedance analysis (CIA) indicates the presence of electrical relaxation in materials. It is noteworthy that relaxation species such as defects may be responsible for electrical conduction. The dielectric behavior of La0.5Ca0.5-xAgxMnO3 manganites has a Debye-like relaxation with a sharp decrease in the real part of permittivity at a frequency where the imaginary part of permittivity (ε'') and tg δ plots versus frequency demonstrate a relaxation peak. The Debye-like relaxation is explained by Maxwell-Wagner (MW) polarization. Experimental results are found to be in good agreement with the Smit and Wijn theory.

Relationship between anisotropies of permeability, electrical conductivity, and dielectric permittivity, with application to the Ellenburger dolomite reservoir analog

NASA Astrophysics Data System (ADS)

Kutemi, Titilope F.

The steady-state flow technique was employed to measure the flow rate of clean dry air through thirty core plugs (approximately 1" diameter) of the Ellenburger dolomite, drilled normal and parallel to the dominant fractures. Porosity was estimated by the method of imbibition. Electrical parameters (electrical conductivity and dielectric permittivity) were calculated from electrical resistance and capacitance measured as a function of frequency (100 Hz, 120 Hz, 1 KHz, and 10 KHz) and saturation (dry/ambient and brine saturated conditions). Another set of permeability data obtained by the method of pressure decay on similar samples was used for correlation. Anisotropies of permeability and electromagnetic parameters were established. Empirical relations between porosity (phi), permeability (k), electrical conductivity (sigma), and dielectric permittivity (epsilon) were defined via cross-plots and linear regressions. Prediction of k from sigma and epsilon was attempted; k from sigma was modeled from a combination of the Archie's relation and the Carman-Kozeny relation. Anisotropic EM responses are sensitive to saturation. Anisotropies of conductivity and permeability were observed to be controlled by the pore micro-structure. Although the rock is fractured, the fracture density appears insufficient to dominate the effects of primary structures in these samples of the Ellenburger dolomite. Model-based prediction of permeability from conductivity is generally unreliable, and is attributed to the underlying assumptions of the models, which are not consistent with the properties of the samples used for this study. Permeability was not predictable from dielectric permittivity.

Practical aspects of complex permittivity reconstruction with neural-network-controlled FDTD modeling of a two-port fixture.

PubMed

Eves, E Eugene; Murphy, Ethan K; Yakovlev, Vadim V

2007-01-01

The paper discusses characteristics of a new modeling-based technique for determining dielectric properties of materials. Complex permittivity is found with an optimization algorithm designed to match complex S-parameters obtained from measurements and from 3D FDTD simulation. The method is developed on a two-port (waveguide-type) fixture and deals with complex reflection and transmission characteristics at the frequency of interest. A computational part is constructed as an inverse-RBF-network-based procedure that reconstructs dielectric constant and the loss factor of the sample from the FDTD modeling data sets and the measured reflection and transmission coefficients. As such, it is applicable to samples and cavities of arbitrary configurations provided that the geometry of the experimental setup is adequately represented by the FDTD model. The practical implementation of the method considered in this paper is a section of a WR975 waveguide containing a sample of a liquid in a cylindrical cutout of a rectangular Teflon cup. The method is run in two stages and employs two databases--first, built for a sparse grid on the complex permittivity plane, in order to locate a domain with an anticipated solution and, second, made as a denser grid covering the determined domain, for finding an exact location of the complex permittivity point. Numerical tests demonstrate that the computational part of the method is highly accurate even when the modeling data is represented by relatively small data sets. When working with reflection and transmission coefficients measured in an actual experimental fixture and reconstructing a low dielectric constant and the loss factor the technique may be less accurate. It is shown that the employed neural network is capable of finding complex permittivity of the sample when experimental data on the reflection and transmission coefficients are numerically dispersive (noise-contaminated). A special modeling test is proposed for validating the results; it confirms that the values of complex permittivity for several liquids (including salt water acetone and three types of alcohol) at 915 MHz are reconstructed with satisfactory accuracy.

ac conductivity in Gd doped Pb(Zr0.53Ti0.47)O3 ceramics

NASA Astrophysics Data System (ADS)

Portelles, J.; Almodovar, N. S.; Fuentes, J.; Raymond, O.; Heiras, J.; Siqueiros, J. M.

2008-10-01

This study is focused in the conduction processes taking place in 0.6 wt % Gd doped lead zirconate titanate samples PbZr0.53Ti0.47O3:Gd (PZT53/47:Gd) in the vicinity of the morphotropic phase boundary. Doped samples show very large dielectric permittivity with respect to that of undoped ones near the transition temperature. The frequency dependent ac conductivity of PZT53/47:Gd ceramics was studied in the 30-450 °C temperature range. X-ray diffraction analyses indicate the incorporation of Gd atoms to the structure. The changes in the dielectric properties as functions of temperature of the doped samples are taken as additional evidence of the incorporation of Gd into the crystal structure. Gd acts as donor center promoting extrinsic n-type conduction. The ac conductivity behavior obeys Jonscher universal relation in the 100 Hz-1 MHz frequency range for temperatures between 30 and 300 °C. The measured conductivity values for Gd doped PZT53/47 are higher than those of pure PZT53/47. According to the correlated barrier hopping model, the preponderant conduction mechanism in the frequency-temperature response was recognized as small polarons hopping mechanism.

Self-focusing and defocusing of Gaussian laser beams in collisional underdense magnetized plasmas with considering the nonlinear ohmic heating and ponderomotive force effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ettehadi Abari, Mehdi; Sedaghat, Mahsa; Shokri, Babak, E-mail: b-shokri@sbu.ac.ir

2015-10-15

The propagation characteristics of a Gaussian laser beam in collisional magnetized plasma are investigated by considering the ponderomotive and ohmic heating nonlinearities. Here, by taking into account the effect of the external magnetic field, the second order differential equation of the dimensionless beam width parameter is solved numerically. Furthermore, the nonlinear dielectric permittivity of the mentioned plasma medium in the paraxial approximation and its dependence on the propagation characteristics of the Gaussian laser pulse is obtained, and its variation in terms of the dimensionless plasma length is analyzed at different initial normalized plasma and cyclotron frequencies. The results show thatmore » the dimensionless beam width parameter is strongly affected by the initial plasma frequency, magnetic strength, and laser pulse intensity. Furthermore, it is found that there exists a certain intensity value below which the laser pulse tends to self focus, while the beam diverges above of this value. In addition, the results confirm that, by increasing the plasma and cyclotron frequencies (plasma density and magnetic strength), the self-focusing effect can occur intensively.« less

Dielectric relaxation dynamics and AC conductivity scaling of metal-organic framework (MOF-5) based polymer electrolyte nanocomposites incorporated with ionic liquid

NASA Astrophysics Data System (ADS)

Dutta, Rituraj; Kumar, A.

2017-10-01

Dielectric relaxation dynamics and AC conductivity scaling of a metal-organic framework (MOF-5) based poly (vinylidene fluoride-co-hexafluoropropylene) (PVdf-HFP) incorporated with 1-Butyl-3-methylimidazolium hexafluorophosphate have been studied over a frequency range of 40 Hz-5 MHz and in the temperature range of 300 K-380 K. High values of dielectric permittivity (~{{\\varepsilon }\\prime} ) having strong dispersion are obtained at low frequency because of interfacial polarization. The real part of the dielectric modulus spectra (M‧) shows no prominent peak, whereas the imaginary part (M″) shows certain peaks, with a reduction in relaxation time (τ) that can be attributed to a non-Debye relaxation mechanism. The spectra also depict both concentration- and temperature-independent scaling behavior. The power law dependent variation of AC conductivity follows the jump relaxation model and reveals activated ion hopping over diffusion barriers. The value of the frequency exponent is observed to decrease with increasing concentration of ionic liquid, indicating the forward hopping of ions in the relaxation process. The AC conductivity scaling curves at different temperatures also depict the temperature-independent relaxation dynamics.

Tunable ferromagnetic resonance in La-Co substituted barium hexaferrites at millimeter wave frequencies

NASA Astrophysics Data System (ADS)

Korolev, Konstantin A.; Wu, Chuanjian; Yu, Zhong; Sun, Ke; Afsar, Mohammed N.; Harris, Vincent G.

2018-05-01

Transmittance measurements have been performed on La-Co substituted barium hexaferrites in millimeter waves. Broadband millimeter-wave measurements have been carried out using the free space quasi-optical spectrometer, equipped with a set of high power backward wave oscillators covering the frequency range of 30 - 120 GHz. Strong absorption zones have been observed in the millimeter-wave transmittance spectra of all La-Co substituted barium hexaferrites due to the ferromagnetic resonance. Linear shift of ferromagnetic resonance frequency as functions of La-Co substitutions have been found. Real and imaginary parts of dielectric permittivity of La-Co substituted barium hexaferrites have been calculated using the analysis of recorded high precision transmittance spectra. Frequency dependences of magnetic permeability of La-Co substituted barium hexaferrites, as well as saturation magnetization and anisotropy field have been determined based on Schlömann's theory for partially magnetized ferrites. La-Co substituted barium hexaferrites have been further investigated by DC magnetization to assess magnetic behavior and compare with millimeter wave data. Consistency of saturation magnetization determined independently by both millimeter wave absorption and DC magnetization have been found for all La-Co substituted barium hexaferrites. These materials seem to be quite promising as tunable millimeter wave absorbers, filters, circulators, based on the adjusting of their substitution parameters.

Self-consistent field model for strong electrostatic correlations and inhomogeneous dielectric media.

PubMed

Ma, Manman; Xu, Zhenli

2014-12-28

Electrostatic correlations and variable permittivity of electrolytes are essential for exploring many chemical and physical properties of interfaces in aqueous solutions. We propose a continuum electrostatic model for the treatment of these effects in the framework of the self-consistent field theory. The model incorporates a space- or field-dependent dielectric permittivity and an excluded ion-size effect for the correlation energy. This results in a self-energy modified Poisson-Nernst-Planck or Poisson-Boltzmann equation together with state equations for the self energy and the dielectric function. We show that the ionic size is of significant importance in predicting a finite self energy for an ion in an inhomogeneous medium. Asymptotic approximation is proposed for the solution of a generalized Debye-Hückel equation, which has been shown to capture the ionic correlation and dielectric self energy. Through simulating ionic distribution surrounding a macroion, the modified self-consistent field model is shown to agree with particle-based Monte Carlo simulations. Numerical results for symmetric and asymmetric electrolytes demonstrate that the model is able to predict the charge inversion at high correlation regime in the presence of multivalent interfacial ions which is beyond the mean-field theory and also show strong effect to double layer structure due to the space- or field-dependent dielectric permittivity.

Effect of dead layer and strain on diffuse phase transition of PLZT relaxor thin films.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tong, S.; Narayanan, M.; Ma, B.

2011-02-01

Bulk relaxor ferroelectrics exhibit excellent permittivity compared to their thin film counterpart, although both show diffuse phase transition (DPT) behavior unlike normal ferroelectrics. To better understand the effect of dead layer and strain on the observed anomaly in the dielectric properties, we have developed relaxor PLZT (lead lanthanum zirconate titanate) thin films with different thicknesses and measured their dielectric properties as a function of temperature and frequency. The effect of dead layer on thin film permittivity has been found to be independent of temperature and frequency, and is governed by the Schottky barrier between the platinum electrode and PLZT. Themore » total strain (thermal and intrinsic) in the film majorly determines the broadening, dielectric peak and temperature shift in the relaxor ferroelectric. The Curie-Weiss type law for relaxors has been further modified to incorporate these two effects to accurately predict the DPT behavior of thin film and bulk relaxor ferroelectrics. The dielectric behavior of thin film is predicted by using the bulk dielectric data from literature in the proposed equation, which agree well with the measured dielectric behavior.« less

The impedance spectroscopy analysis of complex perovskite Sr2YbSbO6

NASA Astrophysics Data System (ADS)

Barua, A.; Maity, S.; Mondal, R.; Kumar, S.

2018-04-01

Herein, we have reported the dielectric properties of single phase monoclinic double perovskite oxide of Sr2YbSbO6 having lattice parameter a=5.79 Å, b=5.79 Å, c=8.19 Å and β = 90.136° with grain size ranging between 0.5 to 2.4 µm. The sample has been synthesized by solid state ceramic method. We have performed the impedence spectroscopic study of the sample in the frequency range of 40 Hz to 5 MHz at various temperatures. The relaxation in the sample is polydispersive in nature and obeys the Cole-Cole model. The values of dielectric permittivity and loss tangent at room temperature are 117.94 and 0.18 respectively. The temperature variation of dc conductivity follows the Arrhenius Law with activation energy 0.2 eV and the conduction mechanism of the sample is governed by p-type polaron hopping. Due to its high dielectric permittivity and low loss tangent the sample can be fruitfully utilized for the fabrication of radio frequency devices.

Preparation, Structural and Dielectric Properties of Solution Grown Polyvinyl Alcohol(PVA) Film

NASA Astrophysics Data System (ADS)

Nangia, Rakhi; Shukla, Neeraj K.; Sharma, Ambika

2017-08-01

Flexible dielectrics with high permittivity have been investigated extensively due to their applications in electronic industry. In this work, structural and electrical characteristics of polymer based film have been analysed. Poly vinyl alcohol (PVA) film was prepared by solution casting method. X-ray diffraction (XRD) characterization technique is used to investigate the structural properties. The semi-crystalline nature has been determined by the analysis of the obtained XRD pattern. Electrical properties of the synthesized film have been analysed from the C-V and I-V curves obtained at various frequencies and temperatures. Low conductivity values confirm the insulating behaviour of the film. However, it is found that conductivity increases with temperature. Also, the dielectric permittivity is found to be higher at lower frequencies and higher temperatures, that proves PVA to be an excellent dielectric material which can be used in interface electronics. Dielectric behaviour of the film has been explained based on dipole orientations to slow and fast varying electric field. However further engineering can be done to modulate the structural, electrical properties of the film.

On the Behavior of Physical Parameters of Aqueous Solutions Affected by the Inerton Field of TESLAR® Technology

NASA Astrophysics Data System (ADS)

Krasnoholovets, Volodymyr; Skliarenko, Sergiy; Strokach, Olexander

We present studies of the behavior of the permittivity of such liquid systems as pure distilled water, alcohol and 50%-aqueous solutions of alcohol as affected by the inerton field generated by a special signal generator contained within a wrist-watch or bracelet made by so-called Teslar® technology. It has been found that the changes are in fact significant. The method employed has allowed us to fix the value of frequency of the field generated by the Teslar® chip. The frequency has been determined to be approximately 8 Hz. The phenomenological consideration and submicroscopic foundations of a significant increase of the permittivity are studied, taking into account an additional interaction, namely, the mass interaction between polar water molecules, which is caused by the inerton field of the Teslar® chip. This is one more proof of Krasnoholovets' concept regarding the existence of a substructure of the matter waves of moving/vibrating entities, i.e. the inerton field, which has been predicted in a series of his previous works.

Rietveld refinement and dielectric properties of (Na{sub 0.5}Bi{sub 0.5}TiO{sub 3})-(Bi{sub 0.8}Ba{sub 0.2}FeO{sub 3}) ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaswan, Kavita, E-mail: kaswan.kavita@gmail.com; Agarwal, Ashish; Sanghi, Sujata

2015-06-24

(1-x)(Na{sub 0.5}Bi{sub 0.5}TiO{sub 3})-x(Bi{sub 0.8}Ba{sub 0.2}FeO{sub 3}) lead free ceramics (NBT, NBT-BBFO; x = 0.0, 0.1 respectively) have been synthesized by conventional solid state reaction method. Crystalline phase of sintered ceramics was investigated at room temperature using X-ray diffraction. Rietveld refinement of XRD data performed by FullProf revealed that both the samples exhibited rhombohedral structure with R3c space group. Dielectric properties of these ceramics were studied at different temperatures in a wide frequency range using impedance analyzer. Dielectric constant and dielectric loss were found to be increase with increase of BBFO content. The prepared ceramics exhibit a broad maximum inmore » dielectric permittivity at 593K and dispersive permittivity at high temperatures. The NBT-BBFO sample shows a relaxor ferroelectric behavior at different frequencies.« less

Dielectric Relaxation Study of Multiferroic BiFe0.95(Ni0.5Ti0.5)0.05O3

NASA Astrophysics Data System (ADS)

Abdelkafi, Z.; Khasskhoussi, G.; Abdelmoula, N.

2018-03-01

The doping of BiFeO3 (BFO) with 5% of Ni and Ti to form the composition BiFe0.95(Ni0.5Ti0.5)0.05O3 (BFNT05) was prepared via a solid state reaction technique. X-ray diffraction (XRD) shows that the prepared ceramic has a pure-phase perovskite structure with rhombohedral symmetry. Thermal evolution of the permittivity reveals a large value of permittivity accompanied by a strong dispersion. This evolution indicates a dielectric anomaly at around 520 K near the Néel temperature ( T N), which supports a strong magneto-dielectric coupling. The dielectric dispersion in BFNT05 was studied by the measurement of the permittivity over a wide frequency range from 20 Hz to 1 MHz at different temperatures 300-700 K. The experimental dielectric data was described by the Cole-Cole relaxation equation modified by introducing the conductivity. Modified impedance and modulus expressions were used successfully as tools to separate the contribution from grains and grain boundaries of BFNT05. The calculated bulk grain conductivity indicated an anomalous behavior near the temperature related to the antiferro-paramagnetic phase transition of the corresponding BFNT05 ceramic. In contrast, this ceramic exhibited a predominant grain boundaries behavior at the studied temperature and frequency range. In this case, they were the elements responsible for dielectric dispersion, and also they played an important role in the improvement of the dielectric behavior of this ceramic. The ac conductivity study confirmed the modified impedance and modulus expressions.

Dielectric Relaxation Study of Multiferroic BiFe0.95(Ni0.5Ti0.5)0.05O3

NASA Astrophysics Data System (ADS)

Abdelkafi, Z.; Khasskhoussi, G.; Abdelmoula, N.

2017-12-01

The doping of BiFeO3 (BFO) with 5% of Ni and Ti to form the composition BiFe0.95(Ni0.5Ti0.5)0.05O3 (BFNT05) was prepared via a solid state reaction technique. X-ray diffraction (XRD) shows that the prepared ceramic has a pure-phase perovskite structure with rhombohedral symmetry. Thermal evolution of the permittivity reveals a large value of permittivity accompanied by a strong dispersion. This evolution indicates a dielectric anomaly at around 520 K near the Néel temperature (T N), which supports a strong magneto-dielectric coupling. The dielectric dispersion in BFNT05 was studied by the measurement of the permittivity over a wide frequency range from 20 Hz to 1 MHz at different temperatures 300-700 K. The experimental dielectric data was described by the Cole-Cole relaxation equation modified by introducing the conductivity. Modified impedance and modulus expressions were used successfully as tools to separate the contribution from grains and grain boundaries of BFNT05. The calculated bulk grain conductivity indicated an anomalous behavior near the temperature related to the antiferro-paramagnetic phase transition of the corresponding BFNT05 ceramic. In contrast, this ceramic exhibited a predominant grain boundaries behavior at the studied temperature and frequency range. In this case, they were the elements responsible for dielectric dispersion, and also they played an important role in the improvement of the dielectric behavior of this ceramic. The ac conductivity study confirmed the modified impedance and modulus expressions.

Two-port transmission line technique for dielectric property characterization of polymer electrolyte membranes.

PubMed

Lu, Zijie; Lanagan, Michael; Manias, Evangelos; Macdonald, Digby D

2009-10-15

Performance improvements of perfluorosulfonic acid membranes, such as Nafion and Flemion, underline a need for dielectric characterization of these materials toward a quantitative understanding of the dynamics of water molecules and protons within the membranes. In this Article, a two-port transmission line technique for measuring the complex permittivity spectra of polymeric electrolytes in the microwave region is described, and the algorithms for permittivity determination are presented. The technique is experimentally validated with liquid water and polytertrafluoroethylene film, whose dielectric properties are well-known. Further, the permittivity spectra of dry and hydrated Flemion SH150 membranes are measured and compared to those of Nafion 117. Two water relaxation modes are observed in the microwave region (0.045-26 GHz) at 25 degrees C. The higher-frequency process observed is identified as the cooperative relaxation of bulk-like water, whose amount was found to increase linearly with water content in the polymer. The lower-frequency process, characterized by longer relaxation times in the range of 20-70 ps, is attributed to water molecules that are loosely bound to sulfonate groups. The loosely bound water amount was found to increase with hydration level at low water content and levels off at higher water contents. Flemion SH150, which has an equivalent weight of 909 g/equiv, displays higher dielectric strengths for both of these water modes as compared to Nafion 117 (equivalent weight of 1100 g/equiv), which probably reflects the effect of equivalent weight on the polymers' hydrated structure, and in particular its effect on the extended ionic cluster domains.

NAPL detection with ground-penetrating radar (Invited)

NASA Astrophysics Data System (ADS)

Bradford, J. H.

2013-12-01

Non-polar organic compounds are common contaminants and are collectively referred to as nonaqueous-phase liquids (NAPLs). NAPL contamination problems occur in virtually every environment on or near the earth's surface and therefore a robust suite of geophysical tools is required to accurately characterize NAPL spills and monitor their remediation. NAPLs typically have low dielectric permittivity and low electric conductivity relative to water. Thus a zone of anomalous electrical properties often occurs when NAPL displaces water in the subsurface pore space. Such electric property anomalies make it possible to detect NAPL in the subsurface using electrical or electromagnetic geophysical methods including ground-penetrating radar (GPR). The GPR signature associated with the presence of NAPL is manifest in essentially three ways. First, the decrease in dielectric permittivity results in increased EM propagation velocity. Second, the decrease in permittivity can significantly change reflectivity. Finally, electric conductivity anomalies lead to anomalous GPR signal attenuation. The conductivity anomaly may be either high or low depending on the state of NAPL degradation, but with either high or low conductivity, GPR attenuation analysis can be a useful tool for identifying contaminated-zones. Over the past 15 years I have conducted numerous modeling, laboratory, and field tests to investigate the ability to use GPR to measure NAPL induced anomalies. The emphasis of this work has been on quantitative analysis to characterize critical source zone parameters such as NAPL concentration. Often, the contaminated zones are below the conventional resolution of the GPR signal and require thin layer analysis. Through a series of field examples, I demonstrate 5 key GPR analysis tools that can help identify and quantify NAPL contaminants. These tools include 1) GPR velocity inversion from multi-fold data, 2) amplitude vs offset analysis, 3) spectral decomposition, 4) frequency dependent attenuation analysis, and 5) reflectivity inversion. Examples are taken from a variety of applications that include oil spills on the ocean, oil spills on and under sea ice, and both LNAPL and DNAPL contaminated groundwater systems. Many factors conspire to complicate field data analysis, yet careful analysis and integration of multiple techniques has proven robust. Use of these methods in practical application has been slow to take root. Nonetheless, a best practices working model integrates geophysics from the outset and mirrors the approach utilized in hydrocarbon exploration. This model ultimately minimizes site characterization and remediation costs.

High permittivity and low loss ceramics in the BaO-SrO-Nb{sub 2}O{sub 5} system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sreemoolanadhan, H.; Sebastian, M.T.; Mohanan, P.

1995-06-01

A new group of compounds with composition (Ba{sub 5{minus}X}Sr{sub x})Nb{sub 4}O{sub 15}, having high permittivity and low loss have been prepared and characterized in the microwave frequency region. X-ray diffraction studies showed that monophase compound existed for all values of x from 0 to 5. Microwave dielectric properties such as {var_epsilon}{sub r} and {tau}{sub f} showed smooth variation with x, while the unloaded quality factor (Q{sub u}) showed remarkable improvement with x. A range of ceramic dielectric resonators (DR) with 40 < {var_epsilon}{sub r} < 50, {minus}10 < {tau}{sub f} < +10 and Q {times} f > 10,000 can bemore » obtained in this system.« less

Magnetoelectric behavior of carbonyl iron mixed Mn oxide-coated ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Ahad, Faris B. Abdul; Lee, Shang-Fan; Hung, Dung-Shing; Yao, Yeong-Der; Yang, Ruey-Bin; Lin, Chung-Kwei; Tsay, Chien-Yie

2010-05-01

The dielectric and magnetic properties of manganese oxide-coated Fe3O4 nanoparticles (NPs) were measured by the cavity perturbation method at x-band microwave frequencies ranging from 7-12.5 GHz with controlled external magnetic field up to 2.2 kOe at room temperature. Different ratios (5%, 10%, and 20% by weight) of coated NPs were prepared by sol-gel method then mixed with carbonyl iron powder in epoxy matrix. The saturation magnetization is inversely proportional to the NPs ratio in the mixture between 150 and 180 emu/g. The real part of the permittivity decreased with increasing NPs concentration, but the permittivity change by magnetic field increased. The tunability behavior is explained by insulator-ferromagnetic interface magnetoelectricity and the large surface volume ratio for the NPs.

Dielectrophoretic spectroscopy using a microscopic electrode array

NASA Astrophysics Data System (ADS)

Kirmani, Syed Abdul Mannan; Gudagunti, Fleming Dackson; Velmanickam, Logeeshan; Nawarathna, Dharmakeerthi; Lima, Ivan T.

2017-02-01

Dielectrophoresis (DEP) is a commonly used technique in biomedical engineering to manipulate biomolecules. DEP is defined as the force acting on dielectric particles when they are exposed to non-uniform electric fields. DEP effect can be divided in three categories: positive (dielectric particles are attracted to the electrodes), negative, and zero force DEP. The cross-over frequency is the frequency in which the DEP force is equal to zero. The cross-over frequency depends on the conductivity and the permittivity of the particles and of the suspended medium. The DEP cross-over frequency has been utilized in detecting/quantifying biomolecules. A manual procedure is commonly used to estimate the cross-over frequency of biomolecules. Therefore, the accuracy of this detection method is significantly limited. To address this issue, we designed and tested an automated procedure to carry out DEP spectroscopy in dielectric particles dissolved in a biological buffer solution. Our method efficiently measures the effect of the DEP force through a live video feed from the microscope camera and performs real-time image processing. It records the change in the fluorescence emission as the system automatically scans the electric frequency of the function generator over a specified time interval. We demonstrated the effectiveness of the method by extracting the crossover frequencies and the DEP spectrum of polystyrene beads with blue color dye (1000 nm diameter) and green fluorescent polystyrene beads with 500 nm diameter using this procedure. This approach can lead to the development of a biosensor with significantly higher sensitivity than existing detection methods.

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.

Synchronized conductivity modulation to realize broadband lossless magnetic-free non-reciprocity.

PubMed

Dinc, Tolga; Tymchenko, Mykhailo; Nagulu, Aravind; Sounas, Dimitrios; Alu, Andrea; Krishnaswamy, Harish

2017-10-06

Recent research has explored the spatiotemporal modulation of permittivity to break Lorentz reciprocity in a manner compatible with integrated-circuit fabrication. However, permittivity modulation is inherently weak and accompanied by loss due to carrier injection, particularly at higher frequencies, resulting in large insertion loss, size, and/or narrow operation bandwidths. Here, we show that the presence of absorption in an integrated electronic circuit may be counter-intuitively used to our advantage to realize a new generation of magnet-free non-reciprocal components. We exploit the fact that conductivity in semiconductors provides a modulation index several orders of magnitude larger than permittivity. While directly associated with loss in static systems, we show that properly synchronized conductivity modulation enables loss-free, compact and extremely broadband non-reciprocity. We apply these concepts to obtain a wide range of responses, from isolation to gyration and circulation, and verify our findings by realizing a millimeter-wave (25 GHz) circulator fully integrated in complementary metal-oxide-semiconductor technology.Optical non-reciprocity achieved through refractive index modulation can have its challenges and limitations. Here, Dinc et al. introduce the concept of non-reciprocity based on synchronized spatio-temporal modulation of conductivity to achieve different types of non-reciprocal functionality.

Single-resonator double-negative metamaterial

DOEpatents

Warne, Larry K.; Basilio, Lorena I.; Langston, William L.; Johnson, William A.; Ihlefeld, Jon; Ginn, III, James C.; Clem, Paul G.; Sinclair, Michael B.

2016-06-21

Resonances can be tuned in dielectric resonators in order to construct single-resonator, negative-index metamaterials. For example, high-contrast inclusions in the form of metallic dipoles can be used to shift the first electric resonance down (in frequency) to the first magnetic resonance, or alternatively, air splits can be used to shift the first magnetic resonance up (in frequency) near the first electric resonance. Degenerate dielectric designs become especially useful in infrared- or visible-frequency applications where the resonator sizes associated with the lack of high-permittivity materials can become of sufficient size to enable propagation of higher-order lattice modes in the resulting medium.

Excitation of THz hybrid modes in an elliptical dielectric rod waveguide with a cold collisionless unmagnetized plasma column by an annular electron beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rahmani, Z., E-mail: z.rahmani@kashanu.ac.ir; Safari, S.; Heidari-Semiromi, E.

2016-06-15

The dispersion relation of electromagnetic waves propagating in an elliptical plasma waveguide with a cold collisionless unmagnetized plasma column and a dielectric rod is studied analytically. The frequency spectrum of the hybrid waves and the growth rate for excitation of the waves by a thin annular relativistic elliptical electron beam (TAREEB) is obtained. The effects of relative permittivity constant of dielectric rod, geometrical dimensions, plasma frequency, accelerating voltage, and current density of TAREEB on the growth rate and frequency spectra of the waveguide will be investigated.

Properties of highly (100) oriented Pb(Mg1/3,Nb2/3)O3-PbTiO3 films on LaNiO3 bottom electrodes

NASA Astrophysics Data System (ADS)

Li, Y. W.; Hu, Z. G.; Yue, F. Y.; Yang, G. Y.; Shi, W. Z.; Meng, X. J.; Sun, J. L.; Chu, J. H.

2007-12-01

The 70%Pb(Mg1/3,Nb2/3)O3-30%PbTiO3 (PMNT) films have been fabricated on LaNiO3 (LNO) coated silicon substrate. The conductive LNO films act as a seed layer for the growth of PMNT films, which depresses the formation of pyrochlore phase and induces the high (100) preferred orientation of perovskite PMNT films. Compared with the PMNT films grown on platinum bottom electrode, the ferroelectric properties of PMNT films grown on LNO are enhanced. The frequency dependence of complex permittivity from PMNT films on LNO is the conjunct result of polarization relaxation and movement of oxygen vacancy, which can be fitted by the function containing Debye and universal dielectric response models, respectively.

Dielectric properties of lung tissue as a function of air content.

PubMed

Nopp, P; Rapp, E; Pfützner, H; Nakesch, H; Ruhsam, C

1993-06-01

Dielectric measurements were made on lung samples with different electrode systems in the frequency range 5 kHz-100 kHz. In the case of plate electrodes and spot electrodes, the effects of electrode polarization were partly corrected. An air filling factor F is defined, which is determined from the mass and volume of the sample. The results indicate that the electrical properties of lung tissue are highly dependent on the condition of the tissue. Furthermore they show that the conductivity sigma as well as the relative permittivity epsilon r decreases with increasing F. This is discussed using histological material. Using a simple theoretical model, the decrease of sigma and epsilon r is explained by the thinning of the alveolar walls as well as by the deformation of the epithelial cells and blood vessels through the expansion of the alveoli.

Interaction of gold nanostars with neuronal cells and single negative terahertz metamaterials with barium titanate resonators

NASA Astrophysics Data System (ADS)

Kereselidze, Zurab

As the title implies, this dissertation covers two independent topics. The first topic is concerned with biomedical applications of nanoparticles while the second topic presents our results in developing all-dielectric single negative metamaterials at terahertz frequencies. In recent years, the interest in using nanoparticles for biomedical applications has greatly increased. Therefore, there is a need to understand the mechanism of interactions as well as any non-lethal effects nanoparticles may have on biological systems. The first part of this dissertation is focused on advancing the field of nanomedicine by developing gold nanostars with a surface plasmon resonance in the infrared that can be used for photothermal ablation. In addition it seeks to quantify the effect gold nanostars have on the firing rate of neuronal cells. The terahertz (THz) region of the electromagnetic spectrum is located between microwaves and infrared where 1 THz corresponds to wavelengths of 300 microns and energies of 3 meV. There are several emerging applications for THz technology spanning biomedical and security imaging, chemical/biological sensing and communications. However, the development of these applications has been hindered because of the lack of electrically and magnetically active natural materials at these frequencies. By designing all-dielectric resonators in which we take advantage of Mie resonances, we can construct metamaterials with effective negative permeabilities and permittivities. In the second topic of this dissertation we present our results developing all-dielectric metamaterials with single negative values. Using a commercial-grade simulator based on the finite-difference time-domain method, we obtained the scattering parameters of the resonators. From the S parameters, we calculated the effective permittivity and permeability of the metamaterials. Using realistic values for the constituent dielectric's permittivity and loss tangent we performed a systematic study of two different resonator geometries: rectangular and triangular prisms. We varied the resonator dimensions, their periodicity and the orientation of the polarization of the incident electric field and were able to obtain negative permeabilities for the rectangular prisms and negative permittivities for the triangular prisms for both orientations of the electric field. Increasing the loss tangent in the rectangular prisms has the effect of removing the region of negative permeabilities.

SYNTHESIS OF NOVEL ALL-DIELECTRIC GRATING FILTERS USING GENETIC ALGORITHMS

NASA Technical Reports Server (NTRS)

Zuffada, Cinzia; Cwik, Tom; Ditchman, Christopher

1997-01-01

We are concerned with the design of inhomogeneous, all dielectric (lossless) periodic structures which act as filters. Dielectric filters made as stacks of inhomogeneous gratings and layers of materials are being used in optical technology, but are not common at microwave frequencies. The problem is then finding the periodic cell's geometric configuration and permittivity values which correspond to a specified reflectivity/transmittivity response as a function of frequency/illumination angle. This type of design can be thought of as an inverse-source problem, since it entails finding a distribution of sources which produce fields (or quantities derived from them) of given characteristics. Electromagnetic sources (electric and magnetic current densities) in a volume are related to the outside fields by a well known linear integral equation. Additionally, the sources are related to the fields inside the volume by a constitutive equation, involving the material properties. Then, the relationship linking the fields outside the source region to those inside is non-linear, in terms of material properties such as permittivity, permeability and conductivity. The solution of the non-linear inverse problem is cast here as a combination of two linear steps, by explicitly introducing the electromagnetic sources in the computational volume as a set of unknowns in addition to the material unknowns. This allows to solve for material parameters and related electric fields in the source volume which are consistent with Maxwell's equations. Solutions are obtained iteratively by decoupling the two steps. First, we invert for the permittivity only in the minimization of a cost function and second, given the materials, we find the corresponding electric fields through direct solution of the integral equation in the source volume. The sources thus computed are used to generate the far fields and the synthesized triter response. The cost function is obtained by calculating the deviation between the synthesized value of reflectivity/transmittivity and the desired one. Solution geometries for the periodic cell are sought as gratings (ensembles of columns of different heights and widths), or combinations of homogeneous layers of different dielectric materials and gratings. Hence the explicit unknowns of the inversion step are the material permittivities and the relative boundaries separating homogeneous parcels of the periodic cell.

Generation mechanism of negative permittivity and Kramers-Kronig relations in BaTiO3/Y3Fe5O12 multiferroic composites

NASA Astrophysics Data System (ADS)

Wang, Zhongyang; Sun, Kai; Xie, Peitao; Liu, Yao; Fan, Runhua

2017-09-01

Recently, negative parameters such as negative permittivity and negative permeability have been attracting extensive attention for their unique electromagnetic properties. Usually, negative permittivity is well achieved by plasma oscillation of free electrons in conductor-insulator composites or metamaterials, while some attention has been paid to attaining negative permittivity in ceramics to reduce dielectric loss. In this paper, negative permittivity in barium titanate and yttrium iron garnet composites are reported which was well fitted by the Lorentz model. Further, negative permittivity behavior was verified via Kramers-Kronig relations, and it revealed that the causal principle still valid for negative permittivity resulted from dielectric resonance. The interrelationships among negative permittivity, capacitive-inductive transition and ac conductivity are discussed.

Transverse-electric plasmonic modes of cylindrical graphene-based waveguide at near-infrared and visible frequencies

PubMed Central

Kuzmin, Dmitry A.; Bychkov, Igor V.; Shavrov, Vladimir G.; Kotov, Leonid N.

2016-01-01

Transverse-electric (TE) surface plasmons (SPs) are very unusual for plasmonics phenomenon. Graphene proposes a unique possibility to observe these plasmons. Due to transverse motion of carriers, TE SPs speed is usually close to bulk light one. In this work we discuss conditions of TE SPs propagation in cylindrical graphene-based waveguides. We found that the negativity of graphene conductivity’s imaginary part is not a sufficient condition. The structure supports TE SPs when the core radius of waveguide is larger than the critical value Rcr. Critical radius depends on the light frequency and the difference of permittivities inside and outside the waveguide. Minimum value of Rcr is comparable with the wavelength of volume wave and corresponds to interband carriers transition in graphene. We predict that use of multilayer graphene will lead to decrease of critical radius. TE SPs speed may differ more significantly from bulk light one in case of epsilon-near-zero core and shell of the waveguide. Results may open the door for practical applications of TE SPs in optics, including telecommunications. PMID:27225745

Parametric study of the physical properties of hydrate-bearing sand, silt, and clay sediments: 1. Electromagnetic properties

USGS Publications Warehouse

Lee, J.Y.; Santamarina, J.C.; Ruppel, C.

2010-01-01

The marked decrease in bulk electrical conductivity of sediments in the presence of gas hydrates has been used to interpret borehole electrical resistivity logs and, to a lesser extent, the results of controlled source electromagnetic surveys to constrain the spatial distribution and predicted concentration of gas hydrate in natural settings. Until now, an exhaustive laboratory data set that could be used to assess the impact of gas hydrate on the electromagnetic properties of different soils (sand, silt, and clay) at different effective stress and with different saturations of hydrate has been lacking. The laboratory results reported here are obtained using a standard geotechnical cell and the hydrate-formed tetrahydrofuran (THF), a liquid that is fully miscible in water and able to produce closely controlled saturations of hydrate from dissolved phase. Both permittivity and electrical conductivity are good indicators of the volume fraction of free water in the sediment, which is in turn dependent on hydrate saturation. Permittivity in the microwave frequency range is particularly predictive of free water content since it is barely affected by ionic concentration, pore structure, and surface conduction. Electrical conductivity (or resistivity) is less reliable for constraining water content or hydrate saturation: In addition to fluid-filled porosity, other factors, such as the ionic concentration of the pore fluid and possibly other conduction effects (e.g., surface conduction in high specific surface soils having low conductivity pore fluid), also influence electrical conductivity.

Nonstoichiometric control of tunnel-filling order, thermal expansion, and dielectric relaxation in tetragonal tungsten Bronzes Ba0.5-xTaO3-x.

PubMed

Pan, Fengjuan; Li, Xiaohui; Lu, Fengqi; Wang, Xiaoming; Cao, Jiang; Kuang, Xiaojun; Véron, Emmanuel; Porcher, Florence; Suchomel, Matthew R; Wang, Jing; Allix, Mathieu

2015-09-21

Ordering of interpolated Ba(2+) chains and alternate Ta-O rows (TaO)(3+) in the pentagonal tunnels of tetragonal tungsten bronzes (TTB) is controlled by the nonstoichiometry in the highly nonstoichiometric Ba0.5-xTaO3-x system. In Ba0.22TaO2.72, the filling of Ba(2+) and (TaO)(3+) groups is partially ordered along the ab-plane of the simple TTB structure, resulting in a √2-type TTB superstructure (Pbmm), while in Ba0.175TaO2.675, the pentagonal tunnel filling is completely ordered along the b-axis of the simple TTB structure, leading to a triple TTB superstructure (P21212). Both superstructures show completely empty square tunnels favoring Ba(2+) conduction and feature unusual accommodation of Ta(5+) cations in the small triangular tunnels. In contrast with stoichiometric Ba6GaTa9O30, which shows linear thermal expansion of the cell parameters and monotonic decrease of permittivity with temperature within 100-800 K, these TTB superstructures and slightly nonstoichiometric simple TTB Ba0.4TaO2.9 display abnormally broad and frequency-dependent extrinsic dielectric relaxations in 10(3)-10(5) Hz above room temperature, a linear deviation of the c-axis thermal expansion around 600 K, and high dielectric permittivity ∼60-95 at 1 MHz at room temperature.

Structural and electrical characteristics of Bi2YTiVO9 ceramic

NASA Astrophysics Data System (ADS)

Gupta, Prabhasini; Padhee, Rajib; Mahapatra, P. K.; Choudhary, R. N. P.

2018-04-01

Studies of structural and electrical characteristics of a member of the Aurivillius structural family (Bi2YTiVO9), prepared by a standard ceramics technology, have been carried out. The phase-pure compound is found to crystallize in the orthorhombic crystal system. The dielectric constant remains around 200 in the studied frequency range of (1 kHz to 1 MHz) and in a temperature range from room temperature to 200 °C. The loss tangent remains in the range of 0.0236 to 0.0056 at room temperature and 0.081 to 0.009 at 200 °C in the same frequency range. The room temperature hysteresis loop exhibits the ferroelectric nature of the sample with remnant polarization of 0.025 μC/cm2 at the coercive field of 4.880 kV cm‑1. The experimental data obtained from Cole-Cole plot on static as well as infinitely high-frequency permittivity, relaxation time and relaxation distribution parameters are used to simulate ε‧, ε″and tanδ which match nicely with experimental data. The conductivity can be explained on the basis of Correlated Barrier Hopping (CBH) model. With 30.92% tenability and a figure of merit of 13 at room temperature and 1 kHz frequency, combined with a stable relative permittivity around 200 with a maximum variation of 6% over a temperature range of 200 °C and low loss tangent, the compound might have some tenability applications.

Polariton excitation in epsilon-near-zero slabs: Transient trapping of slow light

NASA Astrophysics Data System (ADS)

Ciattoni, Alessandro; Marini, Andrea; Rizza, Carlo; Scalora, Michael; Biancalana, Fabio

2013-05-01

We numerically investigate the propagation of a spatially localized and quasimonochromatic electromagnetic pulse through a slab with a Lorentz dielectric response in the epsilon-near-zero regime, where the real part of the permittivity vanishes at the pulse carrier frequency. We show that the pulse is able to excite a set of virtual polariton modes supported by the slab, with the excitation undergoing a generally slow damping due to absorption and radiation leakage. Our numerical and analytical approaches indicate that in its transient dynamics the electromagnetic field displays the very same enhancement of the field component perpendicular to the slab, as in the monochromatic regime. The transient trapping is inherently accompanied by a significantly reduced group velocity ensuing from the small dielectric permittivity, thus providing an alternative platform for achieving control and manipulation of slow light.

Textile inspired flexible metamaterial with negative refractive index

NASA Astrophysics Data System (ADS)

Burgnies, L.; Lheurette, É.; Lippens, D.

2015-04-01

This work introduces metallo-dielectric woven fabric as a metamaterial for phase-front manipulation. Dispersion diagram as well as effective medium parameters retrieved from reflection and transmission coefficients point out negative values of refractive index. By numerical simulations, it is evidenced that a pair of meandered metallic wires, arranged in a top to bottom configuration, can yield to a textile metamaterial with simultaneously negative permittivity and permeability. While the effective negative permittivity stems from the metallic grid arrangement, resonating current loop resulting from the top to bottom configuration of two meandered metallic wires in near proximity produces magnetic activity with negative permeability. By adjusting the distance between pairs of metallic wires, the electric plasma frequency can be shifted to overlap the magnetic resonance. Finally, it is shown that the woven metamaterial is insensitive to the incident angle up to around 60°.

Stick slip, charge separation and decay

USGS Publications Warehouse

Lockner, D.A.; Byerlee, J.D.; Kuksenko, V.S.; Ponomarev, A.V.

1986-01-01

Measurements of charge separation in rock during stable and unstable deformation give unexpectedly large decay times of 50 sec. Time-domain induced polarization experiments on wet and dry rocks give similar decay times and suggest that the same decay mechanisms operate in the induced polarization response as in the relaxation of charge generated by mechanical deformation. These large decay times are attributed to electrochemical processes in the rocks, and they require low-frequency relative permittivity to be very large, in excess of 105. One consequence of large permittivity, and therefore long decay times, is that a significant portion of any electrical charge generated during an earthquake can persist for tens or hundreds of seconds. As a result, electrical disturbances associated with earthquakes should be observable for these lengths of time rather than for the milliseconds previously suggested. ?? 1986 Birka??user Verlag.

Coherent light scattering of heterogeneous randomly rough films and effective medium in the theory of electromagnetic wave multiple scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berginc, G

2013-11-30

We have developed a general formalism based on Green's functions to calculate the coherent electromagnetic field scattered by a random medium with rough boundaries. The approximate expression derived makes it possible to determine the effective permittivity, which is generalised for a layer of an inhomogeneous random medium with different types of particles and bounded with randomly rough interfaces. This effective permittivity describes the coherent propagation of an electromagnetic wave in a random medium with randomly rough boundaries. We have obtained an expression, which contains the Maxwell – Garnett formula at the low-frequency limit, and the Keller formula; the latter hasmore » been proved to be in good agreement with experiments for particles whose dimensions are larger than a wavelength. (coherent light scattering)« less

Near surface bulk density estimates of NEAs from radar observations and permittivity measurements of powdered geologic material

NASA Astrophysics Data System (ADS)

Hickson, Dylan; Boivin, Alexandre; Daly, Michael G.; Ghent, Rebecca; Nolan, Michael C.; Tait, Kimberly; Cunje, Alister; Tsai, Chun An

2018-05-01

The variations in near-surface properties and regolith structure of asteroids are currently not well constrained by remote sensing techniques. Radar is a useful tool for such determinations of Near-Earth Asteroids (NEAs) as the power of the reflected signal from the surface is dependent on the bulk density, ρbd, and dielectric permittivity. In this study, high precision complex permittivity measurements of powdered aluminum oxide and dunite samples are used to characterize the change in the real part of the permittivity with the bulk density of the sample. In this work, we use silica aerogel for the first time to increase the void space in the samples (and decrease the bulk density) without significantly altering the electrical properties. We fit various mixing equations to the experimental results. The Looyenga-Landau-Lifshitz mixing formula has the best fit and the Lichtenecker mixing formula, which is typically used to approximate planetary regolith, does not model the results well. We find that the Looyenga-Landau-Lifshitz formula adequately matches Lunar regolith permittivity measurements, and we incorporate it into an existing model for obtaining asteroid regolith bulk density from radar returns which is then used to estimate the bulk density in the near surface of NEA's (101955) Bennu and (25143) Itokawa. Constraints on the material properties appropriate for either asteroid give average estimates of ρbd = 1.27 ± 0.33g/cm3 for Bennu and ρbd = 1.68 ± 0.53g/cm3 for Itokawa. We conclude that our data suggest that the Looyenga-Landau-Lifshitz mixing model, in tandem with an appropriate radar scattering model, is the best method for estimating bulk densities of regoliths from radar observations of airless bodies.

High-K (Ba0.8Bi0.2)(Zn0.1Ti0.9)O3 ceramics for high-temperature capacitor applications.

PubMed

Raengthon, Natthaphon; Cann, David P

2011-09-01

Solid solutions of BaTiO(3)-Bi(Zn(1/2)Ti(1/2))O(3) were investigated for high-temperature capacitor applications. Compositions close to 0.8BaTiO(3)-0.2Bi(Zn(1/2)Ti(1/2))O(3) revealed pseudo-cubic symmetry and showed a linear dielectric response. The existence of a nearly flat temperature dependence of the relative permittivity over the temperature range of 100 to 350°C was also obtained. In this study, the effects of cation non-stoichiometry and doping were investigated in an attempt to optimize the insulation resistance for high-temperature applications. The dielectric response of (Ba(0.8)-xBi(0.2))(Zn(0.1)Ti(0.9)) O(3) ceramics where 0 ≤ X ≤ 0.08, as well as ZrO2- and Mn(2)O(3)-doped ceramics were studied. The optimum compositions exhibited a relative permittivity in excess of 1150 with a low loss tangent (tan δ < 0.05) that persisted up to a temperature of 460δC. The temperature dependence of resistivity also revealed the improved insulation resistance of Ba-deficient compositions. Additionally, we suggest that an ionic conduction mechanism is responsible for the degradation of resistivity at high temperatures. The temperature coefficient of permittivity ((τ)K) and the RC time constant were also investigated.

The Radar Effects of Perchlorate-Doped Ice in the Martian Polar Layered Deposits

NASA Astrophysics Data System (ADS)

Stillman, D.; Winebrenner, D. P.; Grimm, R. E.; Pathare, A.

2010-12-01

The presence of perchlorate in soil at near-polar latitudes on Mars suggests that dust in the ice of the North Polar Layered Deposits (NPLD) may introduce perchlorate impurities to that ice. Because eutectic temperatures of perchlorate salts range as low as 206 K (for magnesium perchlorate), perchlorate doping of NPLD ice may result in grain-scale liquid veins and softening of ice rheology at temperatures comparable to those computed for the base of the NPLD in the present climate. Any such softening would be important for understanding how processes including ice flow have shaped the NPLD. Observable consequences of such softening, or of the combination of perchlorate doping and temperatures that could cause softening, are thus similarly important. In particular, the dielectric properties of perchlorate-laden ice in a temperature gradient will change relatively rapidly at the point in the gradient near the eutectic temperature. Here we investigate the radar reflectivity of such a eutectic transition in ice with a model in which perchlorate concentration is constant and temperature varies linearly with depth in the ice. We have conducted measurements of the complex permittivity of Mg and Na perchlorate-doped ice over a range of temperatures (183 - 273 K) and concentrations. Below the eutectic temperature, the perchlorate-doped ice has electrical properties similar to that of choride-doped ice. However, above the eutectic temperature, some of the ice melts forming liquid at triple junctions. At concentrations above 3 mM, the liquid at triple junctions become connected forming brine channels, which greatly increase the dc conductivity and radar attenuation. At concentrations below 3 mM, the liquid at triple junctions are not connected and do not affect the dc conductivity. However, the liquid H2O molecules are able to rotate their permanent dipole at radar frequencies, thus causing an increase in radar attenuation. The MARSIS and SHARAD attenuation rates increase with temperature as the strength of the loss increases with a greater amount of liquid water even though the relaxation frequency (maximum loss) shifts to higher frequencies. We combine our electrical property measurements with a model for radar reflection from a continuously-varying dielectric profile. Because the change in permittivity occurs over a range of depths depending on the value of the temperature gradient, radar detectability of the eutectic transition depends on the radar frequency as well as gradient and concentration values. We compute expected radar echo strengths for MARSIS and SHARAD and depths relative to the bed at which transitions may be expected, to address whether information of direct rheological relevance may be available from those instruments.

Nonlinear dielectric response and transient current: An effective potential for ferroelectric domain wall displacement

NASA Astrophysics Data System (ADS)

Placeres Jiménez, Rolando; Pedro Rino, José; Marino Gonçalves, André; Antonio Eiras, José

2013-09-01

Ferroelectric domain walls are modeled as rigid bodies moving under the action of a potential field in a dissipative medium. Assuming that the dielectric permittivity follows the dependence ɛ '∝1/(α+βE2), it obtained the exact expression for the effective potential. Simulations of polarization current correctly predict a power law. Such results could be valuable in the study of domain wall kinetic and ultrafast polarization processes. The model is extended to poled samples allowing the study of nonlinear dielectric permittivity under subswitching electric fields. Experimental nonlinear data from PZT 20/80 thin films and Fe+3 doped PZT 40/60 ceramic are reproduced.

Heavily loaded ferrite-polymer composites to produce high refractive index materials at centimetre wavelengths

NASA Astrophysics Data System (ADS)

Parke, L.; Hooper, I. R.; Hicken, R. J.; Dancer, C. E. J.; Grant, P. S.; Youngs, I. J.; Sambles, J. R.; Hibbins, A. P.

2013-10-01

A cold-pressing technique has been developed for fabricating composites composed of a polytetrafluoroethylene-polymer matrix and a wide range of volume-fractions of MnZn-ferrite filler (0%-80%). The electromagnetic properties at centimetre wavelengths of all prepared composites exhibited good reproducibility, with the most heavily loaded composites possessing simultaneously high permittivity (180 ± 10) and permeability (23 ± 2). The natural logarithm of both the relative complex permittivity and permeability shows an approximately linear dependence with the volume fraction of ferrite. Thus, this simple method allows for the manufacture of bespoke materials required in the design and construction of devices based on the principles of transformation optics.

A large-scale measurement of dielectric properties of normal and malignant colorectal tissues obtained from cancer surgeries at Larmor frequencies.

PubMed

Li, Zhou; Deng, Guanhua; Li, Zhe; Xin, Sherman Xuegang; Duan, Song; Lan, Maoying; Zhang, Sa; Gao, Yixin; He, Jun; Zhang, Songtao; Tang, Hongming; Wang, Weiwei; Han, Shuai; Yang, Qing X; Zhuang, Ling; Hu, Jiani; Liu, Feng

2016-11-01

Knowledge of dielectric properties of malignant human tissues is necessary for the recently developed magnetic resonance (MR) technique called MR electrical property tomography. This technique may be used in early tumor detection based on the obvious differentiation of the dielectric properties between normal and malignant tissues. However, the dielectric properties of malignant human tissues in the scale of the Larmor frequencies are not completely available in the literature. In this study, the authors focused only on the dielectric properties of colorectal tumor tissue. The dielectric properties of 504 colorectal malignant samples excised from 85 patients in the scale of the Larmor frequencies were measured using the precision open-ended coaxial probe method. The obtained complex-permittivity data were fitted to the single-pole Cole-Cole model. The median permittivity and conductivity for the malignant tissue sample were 79.3 and 0.881 S/m at 128 MHz, which were 14.6% and 17.0% higher, respectively, than those of normal tissue samples. Significant differences between normal and malignant tissues were found for the dielectric properties (p < 0.05). Experimental results indicated that the dielectric properties were significantly different between normal and malignant tissues for colorectal tissue. This large-scale clinical measurement provides more subtle base data to validate the technique of MR electrical property tomography.

Photonic band gap properties of one-dimensional Thue-Morse all-dielectric photonic quasicrystal

NASA Astrophysics Data System (ADS)

Yue, Chenxi; Tan, Wei; Liu, Jianjun

2018-05-01

In this paper, the photonic band gap (PBG) properties of one-dimensional (1D) Thue-Morse photonic quasicrystal (PQC) S4 structure are theoretically investigated by using transfer matrix method in Bragg condition. The effects of the center wavelength, relative permittivity and incident angle on PBG properties are elaborately analyzed. Numerical results reveal that, in the case of normal incidence, the symmetry and periodicity properties of the photonic band structure are presented. As the center wavelength increases, the PBG center frequency and PBG width decrease while the photonic band structure is always symmetrical about the central frequency and the photonic band structure repeats periodically in the expanding observation frequency range. With the decrease of relative permittivity contrast, the PBG width and the relative PBG width gradually decreases until PBG disappears while the symmetry of the photonic band structure always exists. In the case of oblique incidence, as the incident angle increases, multiple narrow PBGs gradually merge into a wide PBG for the TE mode while for the TM mode, the number of PBG continuously decreases and eventually disappears, i.e., multiple narrow PBGs become a wide passband for the TM mode. The research results will provide a reference for the choice of the material, the incident angle for the PBG properties and its applications of 1D Thue-Morse PQC.

A high frequency electromagnetic impedance imaging system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tseng, Hung-Wen; Lee, Ki Ha; Becker, Alex

2003-01-15

Non-invasive, high resolution geophysical mapping of the shallow subsurface is necessary for delineation of buried hazardous wastes, detecting unexploded ordinance, verifying and monitoring of containment or moisture contents, and other environmental applications. Electromagnetic (EM) techniques can be used for this purpose since electrical conductivity and dielectric permittivity are representative of the subsurface media. Measurements in the EM frequency band between 1 and 100 MHz are very important for such applications, because the induction number of many targets is small and the ability to determine the subsurface distribution of both electrical properties is required. Earlier workers were successful in developing systemsmore » for detecting anomalous areas, but quantitative interpretation of the data was difficult. Accurate measurements are necessary, but difficult to achieve for high-resolution imaging of the subsurface. We are developing a broadband non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using an EM impedance approach similar to the MT exploration technique. Electric and magnetic sensors were tested to ensure that stray EM scattering is minimized and the quality of the data collected with the high-frequency impedance (HFI) system is good enough to allow high-resolution, multi-dimensional imaging of hidden targets. Additional efforts are being made to modify and further develop existing sensors and transmitters to improve the imaging capability and data acquisition efficiency.« less

Microwave resonances in dielectric samples probed in Corbino geometry: simulation and experiment.

PubMed

Felger, M Maximilian; Dressel, Martin; Scheffler, Marc

2013-11-01

The Corbino approach, where the sample of interest terminates a coaxial cable, is a well-established method for microwave spectroscopy. If the sample is dielectric and if the probe geometry basically forms a conductive cavity, this combination can sustain well-defined microwave resonances that are detrimental for broadband measurements. Here, we present detailed simulations and measurements to investigate the resonance frequencies as a function of sample and probe size and of sample permittivity. This allows a quantitative optimization to increase the frequency of the lowest-lying resonance.

Energy conservation of the scattering from one-dimensional random rough surfaces in the high-frequency limit.

PubMed

Pinel, Nicolas; Bourlier, Christophe; Saillard, Joseph

2005-08-01

Energy conservation of the scattering from one-dimensional strongly rough dielectric surfaces is investigated using the Kirchhoff approximation with single reflection and by taking the shadowing phenomenon into account, both in reflection and transmission. In addition, because no shadowing function in transmission exists in the literature, this function is presented here in detail. The model is reduced to the high-frequency limit (or geometric optics). The energy conservation criterion is investigated versus the incidence angle, the permittivity of the lower medium, and the surface rms slope.

Babinet principle applied to the design of metasurfaces and metamaterials.

PubMed

Falcone, F; Lopetegi, T; Laso, M A G; Baena, J D; Bonache, J; Beruete, M; Marqués, R; Martín, F; Sorolla, M

2004-11-05

The electromagnetic theory of diffraction and the Babinet principle are applied to the design of artificial metasurfaces and metamaterials. A new particle, the complementary split rings resonator, is proposed for the design of metasurfaces with high frequency selectivity and planar metamaterials with a negative dielectric permittivity. Applications in the fields of frequency selective surfaces and polarizers, as well as in microwave antennas and filter design, can be envisaged. The tunability of all these devices by an applied dc voltage is also achievable if these particles are etched on the appropriate substrate.

Modeling of layered anisotropic composite material based on effective medium theory

NASA Astrophysics Data System (ADS)

Bao, Yang; Song, Jiming

2018-04-01

In this paper, we present an efficient method to simulate multilayered anisotropic composite material with effective medium theory. Effective permittivity, permeability and orientation angle for a layered anisotropic composite medium are extracted with this equivalent model. We also derive analytical expressions for effective parameters and orientation angle with low frequency (LF) limit, which will be shown in detail. Numerical results are shown in comparing extracted effective parameters and orientation angle with analytical results from low frequency limit. Good agreements are achieved to demonstrate the accuracy of our efficient model.

Frequency scanning capaciflector for capacitively determining the material properties

NASA Technical Reports Server (NTRS)

Campbell, Charles E. (Inventor)

1996-01-01

A capaciflector sensor system scanned in frequency is used to detect the permittivity of the material of an object being sensed. A capaciflector sensor element, coupled to current-measuring voltage follower circuitry, is driven by a frequency swept oscillator and generates an output which corresponds to capacity as a function of the input frequency. This swept frequency information is fed into apparatus e.g. a digital computer for comparing the shape of the capacitance vs. frequency curve against characteristic capacitor vs. frequency curves for a variety of different materials which are stored, for example, in a digital memory of the computer or a database. Using a technique of pattern matching, a determination is made as to the identification of the material. Also, when desirable, the distance between the sensor and the object can be determined.

Design and Characterization of Optical Metamaterials Using Tunable Polarimetric Scatterometry

DTIC Science & Technology

2012-12-01

metamaterial absorber (MMA) [33]. The MMA was found to have an incident angle depend resonance, which was captured with Mm polarimetry measurements...TERMS Dual Rotating Retarder, Polarimetry Scatterometry, Metamaterials, Near-Zero Permittivity 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, Zhijuan; Hu, Bolin; Chen, Yajie, E-mail: y.chen@neu.edu

A series of Z-type and Y-type ferrite composites with various phase fractions were studied for their RF properties including the measurement of permittivity to permeability spectra over a frequency range of 0.1–10 GHz. Phase identification of the ferrite composites' constituents was determined by X-ray diffraction. An effective medium approximation was used to predict the magnetic and dielectric behavior of the composites. The experiments indicated that the composite having 75 vol. % of Z-type ferrite demonstrated a permeability of ∼12 with a nearly equivalent permittivity, yielding a ratio (μ′/ε′) of 0.91 at a frequency range from 0.55 to 0.75 GHz. The dielectric loss (i.e.,more » tan δ{sub ε}) and magnetic loss (i.e., tan δ{sub μ}) were measured to be lower than 0.08 at f = 0.1–1 GHz and 0.29 at f = 0.1–0.7 GHz, respectively. Furthermore, the loss factors, as tan δ{sub ε}/ε′ and tan δ{sub μ}/μ′, were calculated to be 0.003 and 0.02 at 0.65 GHz, respectively.« less

Enhancement mechanism of the additional absorbent on the absorption of the absorbing composite using a type-based mixing rule

NASA Astrophysics Data System (ADS)

Xu, Yonggang; Yuan, Liming; Zhang, Deyuan

2016-04-01

A silicone rubber composite filled with carbonyl iron particles and four different carbonous materials (carbon black, graphite, carbon fiber or multi-walled carbon nanotubes) was prepared using a two-roller mixture. The complex permittivity and permeability were measured using a vector network analyzer at the frequency of 2-18 GHz. Then a type-based mixing rule based on the dielectric absorbent and magnetic absorbent was proposed to reveal the enhancing mechanism on the permittivity and permeability. The enforcement effect lies in the decreased percolation threshold and the changing pending parameter as the carbonous materials were added. The reflection loss (RL) result showed the added carbonous materials enhanced the absorption in the lower frequency range, the RL decrement value being about 2 dB at 4-5 GHz with a thickness of 1 mm. All the added carbonous materials reinforced the shielding effectiveness (SE) of the composites. The maximum increment value of the SE was about 3.23 dB at 0.5 mm and 4.65 dB at 1 mm, respectively. The added carbonous materials could be effective additives for enforcing the absorption and shielding property of the absorbers.

Presentation of a complex permittivity-meter with applications for sensing the moisture and salinity of a porous media.

PubMed

Chavanne, Xavier; Frangi, Jean-Pierre

2014-08-26

This paper describes a sensor dedicated to measuring the vertical profile of the complex permittivity and the temperature of any medium in which sensor electrodes are inserted. Potential applications are the estimate of the humidity and salinity in a porous medium, such as a soil. It consists of vertically-stacked capacitors along two conductive parallel cylinders of 5 cm in diameter and at a 10-cm distance to scan a significant volume of the medium (~1 L). It measures their admittances owing to a self-balanced impedance bridge operating at a frequency in the range of 1-20 MHz, possibly 30 MHz. Thanks to accurate design and electronic circuit theory-based modeling, the determination of the admittances takes into account all distortions due to lead and bridge electromagnetic effects inside the sensor when working at high frequencies. Calibration procedures and uncertainties are presented. The article also describes developments to make the present sensor autonomous on digital acquisition, basic data treatment and energy, as well as able to transfer stored data by a radio link. These steps in progress are prerequisites for a wireless network of sensors.

Classical ferroelectriclike behavior of highly ordered Pb (S c1 /2N b1 /2)O3 studied by dielectric and Brillouin scattering spectroscopy

NASA Astrophysics Data System (ADS)

Sivasubramanian, V.; Subramanian, V.; Kojima, S.

2016-02-01

The ferroelectric phase transition behavior in the highly ordered Pb (S c1 /2N b1 /2) O3 has been investigated by the dielectric and Brillouin spectroscopy. The dielectric permittivity ɛr exhibits a sharp maximum without any frequency dispersion at its Curie temperature Tc. In the temperature range far above Tc, it was noted that the dielectric permittivity exhibits a noticeable deviation from the Curie-Weiss law below the characteristic intermediate temperature T*=500 K , which is common to most of the Pb-based oxide perovskite relaxors. Upon cooling, the frequency of the longitudinal acoustic phonon mode exhibits a remarkable softening towards Tc. The relaxation time of the order parameter calculated using the Landau-Khalatnikov approach was determined to be more than one order of magnitude lower than that of the disordered Pb (S c1 /2N b1 /2)O3 and is very close to that observed in the paraelectric phase of the classical ferroelectric, BaTi O3 . The observed dielectric and relaxation features are qualitatively discussed in terms of the difference in the strength of the random electric fields.

Presentation of a Complex Permittivity-Meter with Applications for Sensing the Moisture and Salinity of a Porous Media

PubMed Central

Chavanne, Xavier; Frangi, Jean-Pierre

2014-01-01

This paper describes a sensor dedicated to measuring the vertical profile of the complex permittivity and the temperature of any medium in which sensor electrodes are inserted. Potential applications are the estimate of the humidity and salinity in a porous medium, such as a soil. It consists of vertically-stacked capacitors along two conductive parallel cylinders of 5 cm in diameter and at a 10-cm distance to scan a significant volume of the medium (∼1 L). It measures their admittances owing to a self-balanced impedance bridge operating at a frequency in the range of 1–20 MHz, possibly 30 MHz. Thanks to accurate design and electronic circuit theory-based modeling, the determination of the admittances takes into account all distortions due to lead and bridge electromagnetic effects inside the sensor when working at high frequencies. Calibration procedures and uncertainties are presented. The article also describes developments to make the present sensor autonomous on digital acquisition, basic data treatment and energy, as well as able to transfer stored data by a radio link. These steps in progress are prerequisites for a wireless network of sensors. PMID:25162233

One-way quasiplanar terahertz absorbers using nonstructured polar dielectric layers

NASA Astrophysics Data System (ADS)

Rodríguez-Ulibarri, P.; Beruete, M.; Serebryannikov, A. E.

2017-10-01

A concept of quasiplanar one-way transparent terahertz absorbers made of linear isotropic materials is presented. The resulting structure consists of a homogeneous absorbing layer of polar dielectric, GaAs, a dispersion-free substrate, and an ultrathin frequency-selective reflector. It is demonstrated that perfect absorption can be obtained for forward illumination, along with total reflection at backward illumination and transparency windows in the adjacent bands. The design is particularized for the polaritonic gap range where permittivity of GaAs varies in a wide range and includes epsilon-near-zero and transparency regimes. The underlying physics can be explained with the aid of a unified equivalent-circuit (EC) analytical model. Perfect matching of input impedance in forward operation and, simultaneously, strong mismatch in the backward case are the universal criteria of one-way absorption. It is shown that perfect one-way absorption can be achieved at rather arbitrary permittivity values, provided these criteria are fulfilled. The EC results are in good agreement with full-wave simulations in a wide range of material and geometrical parameters. The resulting one-way absorbers are very compact and geometrically simple, and enable transparency in the neighboring frequency ranges and, hence, multifunctionality that utilizes both absorption- and transmission-related regimes.

A database for the static dielectric constant of water and steam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernandez, D.P.; Mulev, Y.; Goodwin, A.R.H.

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 assessmentmore » 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.« less

Role of random electric fields in relaxors

PubMed Central

Phelan, Daniel; Stock, Christopher; Rodriguez-Rivera, Jose A.; Chi, Songxue; Leão, Juscelino; Long, Xifa; Xie, Yujuan; Bokov, Alexei A.; Ye, Zuo-Guang; Ganesh, Panchapakesan; Gehring, Peter M.

2014-01-01

PbZr1–xTixO3 (PZT) and Pb(Mg1/3Nb2/3)1–xTixO3 (PMN-xPT) are complex lead-oxide perovskites that display exceptional piezoelectric properties for pseudorhombohedral compositions near a tetragonal phase boundary. In PZT these compositions are ferroelectrics, but in PMN-xPT they are relaxors because the dielectric permittivity is frequency dependent and exhibits non-Arrhenius behavior. We show that the nanoscale structure unique to PMN-xPT and other lead-oxide perovskite relaxors is absent in PZT and correlates with a greater than 100% enhancement of the longitudinal piezoelectric coefficient in PMN-xPT relative to that in PZT. By comparing dielectric, structural, lattice dynamical, and piezoelectric measurements on PZT and PMN-xPT, two nearly identical compounds that represent weak and strong random electric field limits, we show that quenched (static) random fields establish the relaxor phase and identify the order parameter. PMID:24449912

Low temperature dielectric relaxation in ordinary perovskite ferroelectrics: enlightenment from high-energy x-ray diffraction

NASA Astrophysics Data System (ADS)

Ochoa, D. A.; Levit, R.; Fancher, C. M.; Esteves, G.; Jones, J. L.; E García, J.

2017-05-01

Ordinary ferroelectrics exhibit a second order phase transition that is characterized by a sharp peak in the dielectric permittivity at a frequency-independent temperature. Furthermore, these materials show a low temperature dielectric relaxation that appears to be a common behavior of perovskite systems. Tetragonal lead zirconate titanate is used here as a model system in order to explore the origin of such an anomaly, since there is no consensus about the physical phenomenon involved in it. Crystallographic and domain structure studies are performed from temperature dependent synchrotron x-ray diffraction measurement. Results indicate that the dielectric relaxation cannot be associated with crystallographic or domain configuration changes. The relaxation process is then parameterized by using the Vogel-Fulcher-Tammann phenomenological equation. Results allow us to hypothesize that the observed phenomenon is due to changes in the dynamic behavior of the ferroelectric domains related to the fluctuation of the local polarization.

Thermally controlled femtosecond pulse shaping using metasurface based optical filters

NASA Astrophysics Data System (ADS)

Rahimi, Eesa; Şendur, Kürşat

2018-02-01

Shaping of the temporal distribution of the ultrashort pulses, compensation of pulse deformations due to phase shift in transmission and amplification are of interest in various optical applications. To address these problems, in this study, we have demonstrated an ultra-thin reconfigurable localized surface plasmon (LSP) band-stop optical filter driven by insulator-metal phase transition of vanadium dioxide. A Joule heating mechanism is proposed to control the thermal phase transition of the material. The resulting permittivity variation of vanadium dioxide tailors spectral response of the transmitted pulse from the stack. Depending on how the pulse's spectrum is located with respect to the resonance of the band-stop filter, the thin film stack can dynamically compress/expand the output pulse span up to 20% or shift its phase up to 360°. Multi-stacked filters have shown the ability to dynamically compensate input carrier frequency shifts and pulse span variations besides their higher span expansion rates.

Metal Standards for Waveguide Characterization of Materials

NASA Technical Reports Server (NTRS)

Lambert, Kevin M.; Kory, Carol L.

2009-01-01

Rectangular-waveguide inserts that are made of non-ferromagnetic metals and are sized and shaped to function as notch filters have been conceived as reference standards for use in the rectangular- waveguide method of characterizing materials with respect to such constitutive electromagnetic properties as permittivity and permeability. Such standards are needed for determining the accuracy of measurements used in the method, as described below. In this method, a specimen of a material to be characterized is cut to a prescribed size and shape and inserted in a rectangular- waveguide test fixture, wherein the specimen is irradiated with a known source signal and detectors are used to measure the signals reflected by, and transmitted through, the specimen. Scattering parameters [also known as "S" parameters (S11, S12, S21, and S22)] are computed from ratios between the transmitted and reflected signals and the source signal. Then the permeability and permittivity of the specimen material are derived from the scattering parameters. Theoretically, the technique for calculating the permeability and permittivity from the scattering parameters is exact, but the accuracy of the results depends on the accuracy of the measurements from which the scattering parameters are obtained. To determine whether the measurements are accurate, it is necessary to perform comparable measurements on reference standards, which are essentially specimens that have known scattering parameters. To be most useful, reference standards should provide the full range of scattering-parameter values that can be obtained from material specimens. Specifically, measurements of the backscattering parameter (S11) from no reflection to total reflection and of the forward-transmission parameter (S21) from no transmission to total transmission are needed. A reference standard that functions as a notch (band-stop) filter can satisfy this need because as the signal frequency is varied across the frequency range for which the filter is designed, the scattering parameters vary over the ranges of values between the extremes of total reflection and total transmission. A notch-filter reference standard in the form of a rectangular-waveguide insert that has a size and shape similar to that of a material specimen is advantageous because the measurement configuration used for the reference standard can be the same as that for a material specimen. Typically a specimen is a block of material that fills a waveguide cross-section but occupies only a small fraction of the length of the waveguide. A reference standard of the present type (see figure) is a metal block that fills part of a waveguide cross section and contains a slot, the long dimension of which can be chosen to tailor the notch frequency to a desired value. The scattering parameters and notch frequency can be estimated with high accuracy by use of commercially available electromagnetic-field-simulating software. The block can be fabricated to the requisite precision by wire electrical-discharge machining. In use, the accuracy of measurements is determined by comparison of (1) the scattering parameters calculated from the measurements with (2) the scattering parameters calculated by the aforementioned software.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tuhkala, M., E-mail: mtuhkala@ee.oulu.fi; Maček, M.; Siponkoski, T.

Highlights: • Elongated micrometre sized BaTiO{sub 3} particles had strong effect on permittivity. • Effect was significantly stronger compared to μm and nm sized spherical particles. • Properties could be tailored by varying the particle shapes of dielectric powders. • Could be utilized, e.g., in a production of electrical composites for RF applications. - Abstract: The effect of BaTiO{sub 3} particle shape on the properties of 0.98MgTiO{sub 3}–0.02BaTiO{sub 3} composite powders was characterized and analyzed using an indirectly coupled open-ended coaxial cavity resonator at gigahertz frequencies. Elongated micrometre sized BaTiO{sub 3} particles were found to have a significantly stronger effectmore » on permittivity when compared to composite powders having micro and nano sized spherical BaTiO{sub 3} particles. Inclusion permittivities and dielectric loss tangents of composite powders increased from that of pure MgTiO{sub 3} powder, 13.3 and 4.6 × 10{sup −3}, up to 15.7 and 1.7 × 10{sup −2} with needle shaped BaTiO{sub 3} particles, respectively. The presented results give valuable information for tailoring the properties of dielectrics which can be utilized in the vast field of electronic component manufacturing.« less

Calibration-independent measurement of complex permittivity of liquids using a coaxial transmission line

NASA Astrophysics Data System (ADS)

Guoxin, Cheng

2015-01-01

In recent years, several calibration-independent transmission/reflection methods have been developed to determine the complex permittivity of liquid materials. However, these methods experience their own respective defects, such as the requirement of multi measurement cells, or the presence of air gap effect. To eliminate these drawbacks, a fast calibration-independent method is proposed in this paper. There are two main advantages of the present method over those in the literature. First, only one measurement cell is required. The cell is measured when it is empty and when it is filled with liquid. This avoids the air gap effect in the approach, in which the structure with two reference ports connected with each other is needed to be measured. Second, it eliminates the effects of uncalibrated coaxial cables, adaptors, and plug sections; systematic errors caused by the experimental setup are avoided by the wave cascading matrix manipulations. Using this method, three dielectric reference liquids, i.e., ethanol, ethanediol, and pure water, and low-loss transformer oil are measured over a wide frequency range to validate the proposed method. Their accuracy is assessed by comparing the results with those obtained from the other well known techniques. It is demonstrated that this proposed method can be used as a robust approach for fast complex permittivity determination of liquid materials.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chawla, Mahak, E-mail: mahak.chawla@gmail.com; Shekhawat, Nidhi; Aggarwal, Sanjeev

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.more » Relaxation processes were studied by Cole-Cole plot of complex permittivity (real part of complex permittivity, ε′ vs. imaginary part of complex permittivity, ε″). The Cole-Cole plots have also been used to determine static dielectric constant (ε{sub s}), optical dielectric constant (ε{sub ∞}), spreading factor (α), average relaxation time (τ{sub 0}) and molecular relaxation time (τ). 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.« less

In vivo and in situ measurement and modelling of intra-body effective complex permittivity

PubMed Central

Blanes-Vidal, Victoria; Harslund, Jakob L.F.; Ramezani, Mohammad H.; Kjeldsen, Jens; Johansen, Per Michael; Thiel, David; Tarokh, Vahid

2015-01-01

Radio frequency tracking of medical micro-robots in minimally invasive medicine is usually investigated upon the assumption that the human body is a homogeneous propagation medium. In this Letter, the authors conducted various trial programs to measure and model the effective complex permittivity ε in terms of refraction ε′, absorption ε″ and their variations in gastrointestinal (GI) tract organs (i.e. oesophagus, stomach, small intestine and large intestine) and the porcine abdominal wall under in vivo and in situ conditions. They further investigated the effects of irregular and unsynchronised contractions and simulated peristaltic movements of the GI tract organs inside the abdominal cavity and in the presence of the abdominal wall on the measurements and variations of ε′ and ε′′. They advanced the previous models of effective complex permittivity of a multilayer inhomogeneous medium, by estimating an analytical model that accounts for reflections between the layers and calculates the attenuation that the wave encounters as it traverses the GI tract and the abdominal wall. They observed that deviation from the specified nominal layer thicknesses due to non-geometric boundaries of GI tract morphometric variables has an impact on the performance of the authors’ model. Therefore, they derived statistical-based models for ε′ and ε′′ using their experimental measurements. PMID:26713157

In vivo and in situ measurement and modelling of intra-body effective complex permittivity.

PubMed

Nadimi, Esmaeil S; Blanes-Vidal, Victoria; Harslund, Jakob L F; Ramezani, Mohammad H; Kjeldsen, Jens; Johansen, Per Michael; Thiel, David; Tarokh, Vahid

2015-12-01

Radio frequency tracking of medical micro-robots in minimally invasive medicine is usually investigated upon the assumption that the human body is a homogeneous propagation medium. In this Letter, the authors conducted various trial programs to measure and model the effective complex permittivity ε in terms of refraction ε', absorption ε″ and their variations in gastrointestinal (GI) tract organs (i.e. oesophagus, stomach, small intestine and large intestine) and the porcine abdominal wall under in vivo and in situ conditions. They further investigated the effects of irregular and unsynchronised contractions and simulated peristaltic movements of the GI tract organs inside the abdominal cavity and in the presence of the abdominal wall on the measurements and variations of ε' and ε''. They advanced the previous models of effective complex permittivity of a multilayer inhomogeneous medium, by estimating an analytical model that accounts for reflections between the layers and calculates the attenuation that the wave encounters as it traverses the GI tract and the abdominal wall. They observed that deviation from the specified nominal layer thicknesses due to non-geometric boundaries of GI tract morphometric variables has an impact on the performance of the authors' model. Therefore, they derived statistical-based models for ε' and ε'' using their experimental measurements.

Characterization of the relationship of the cure cycle chemistry to cure cycle processing properties

NASA Technical Reports Server (NTRS)

Kranbuehl, D. E.

1986-01-01

Dynamic Dielectric measurements made over a wide range of frequency provide a sensitive and convenient means for monitoring the cure process in thermosets and thermoplastics. The measurement of dielectric relaxation is one of only a few instrumental techniques available for studying molecular properties in both the liquid and solid states. Furthermore, it is probably the only convenient experimental technique for studying the polymerization process of going from a monomeric liquid of varying viscosity to a crosslinked, insoluble, high temperature solid. The objective of the research is to develop on-line dielectric instrumentation for quantitative nondestructive material evaluation and closed loop smart cure cycle control. The key is to relate the chemistry of the cure cycle process to the dielectric properties of the polymer system by correlating the time, temperature, and frequency dependent dielectric measurements with chemical characterization measurements. Measurement of the wide variation in magnitude of the complex permittivity with both frequency and state of cure, coupled with chemical characterization work, have been shown in the laboratory to have the potential to determine: resin quality, composition and age; cure cycle window boundaries; onset of flow and point of maximum flow; extent of and completion of reaction; evolution of volatiles; T sub g; and, crosslinking and molecular weight buildup.

Partial substitution effects on the physical properties of Ba0.67Nd0.22Ti(1-x)SnxO3

NASA Astrophysics Data System (ADS)

Brahem, R.; Rahmouni, H.; Farhat, N.; Costa, L. C.; Khirouni, K.

2015-12-01

Perovskite-ceramics Ba0.67Nd0.22Ti(1-x)SnxO3 (BNTSnx) with 0≤ x≤ 0.10 are synthesized by the conventional solid-state reaction. The diffraction peaks are sharp, indicating well crystallized phases. Ritveld analyses of XRD data show that the samples display a clean single phase without traces of secondary phases. The Scanning electron microscopy micrographs show that more dense structure is formed when increasing tin content and all samples show a similar grain habit with a parallelepipedic structure. The analysis of the dielectric properties permits to suggest the presence of diffuse phase transition in the system. The temperature dependence of the permittivity is well described by the modified Curie-Weiss law. Also, a metal-semiconductor transition is observed at around T_{MS}=220 K and 145 K, respectively for x = 0 and 0.05. For x = 0.1, only a semiconductor behavior is observed and T_{MS} is lower than 80 K. In addition, the frequency dependence of conductance is found to obey to the Jonscher universal power law.

Influence of Clay Content, Mineralogy and Fabric On Radar Frequency Response of Aquifer Materials

NASA Astrophysics Data System (ADS)

West, L. J.; Handley, K.

High frequency electromagnetic methods such as ground penetrating radar (GPR) and time domain reflectometry (TDR) are widely employed to measure water saturation in the vadose zone and water filled porosity in the saturated zone. However, previous work has shown that radar frequency dielectric properties are strongly influenced by clay as well as by water content. They have also shown that that the dielectric response of clay minerals is strongly frequency dependent, and that even a small proportion of clay such as that present in many sandstone aquifers can have a large effect at typi- cal GPR frequencies (around 100MHz). Hence accurate water content/porosity deter- mination requires clay type and content to be taken into account. Reported here are dielectric measurements on clay-sand mixtures, aimed at investigating the influence of clay mineralogy, particle shape, and the geometrical arrangement of the mixture constituents on GPR and TDR response. Dielectric permittivity (at 50-1000MHz) was measured for mixtures of Ottawa Sand and various clay minerals or clay size quartz rock flour, using a specially constructed dielectric cell. Both homogeneous and layered mixtures were tested. The influence of pore water salinity, clay type, and particle arrangement on the dielectric response is interpreted in terms of dielectric dispersion mechanisms. The appropriateness of var- ious dielectric mixing rules such as the Complex Refractive Index Method (CRIM) for determination of water content or porosity from field GPR and TDR data are dis- cussed.

Grain boundary-dominated electrical conduction and anomalous optical-phonon behaviour near the Neel temperature in YFeO3 ceramics

NASA Astrophysics Data System (ADS)

Raut, Subhajit; Babu, P. D.; Sharma, R. K.; Pattanayak, Ranjit; Panigrahi, Simanchalo

2018-05-01

We investigated the anomalous behaviour in the dielectric properties, occurring nearly at room temperature and at elevated temperatures (near the Neel temperature TN) of the polycrystalline samples of YFeO3 (YFO) ceramics. On the prepared YFO ceramics, the magnetic measurements showed the Neel temperature of YFO to be 650 K, below which the compound exhibited the weak ferromagnetic behaviour. X-ray photoelectron spectroscopy (XPS) shows the presence of Fe ions (Fe2+ and Fe3+ states) and also revealed the formation of the oxygen vacancies. The frequency dependence of the complex dielectric constant within the frequency domain of 100 Hz-1 MHz shows the presence of grain dominated dielectric relaxation over the thermal window of 300-373 K. The activation energy Eact.ɛ=0.611 eV extracted from the imaginary permittivity spectrum indicates the involvement of oxygen vacancies in the relaxation process. Above 493 K, the ac conductivity, complex impedance, and modulus studies revealed appreciable conduction and relaxation processes occurring in YFO ceramics with respective activation energies Eac t . σ=1.362 eV and Eac t . Z=1.345 eV , which suggests that the oxygen vacancies are also involved for the anomalous behaviour of the dielectric constant at elevated temperatures. The temperature dependent Raman spectroscopic measurements within the thermal window of 298-698 K showed anomalous variations of the line widths and frequencies of several Raman active modes above 473 K up to the vicinity of TN pointing towards the presence of admixtures of the electron-phonon and spin-phonon coupling in the system. A further study on the thermal variation of the B2g(4) mode frequency with [M(T)/MS]2 shows the occurrence of strong spin-phonon (s-p) coupling, while the line shape shows the presence of the Fano asymmetry, suggesting spin dependent electron-phonon (e-p) coupling in the system below TN.

A system for measuring complex dielectric properties of thin films at submillimeter wavelengths using an open hemispherical cavity and a vector network analyzer.

PubMed

Rahman, Rezwanur; Taylor, P C; Scales, John A

2013-08-01

Quasi-optical (QO) methods of dielectric spectroscopy are well established in the millimeter and submillimeter frequency bands. These methods exploit standing wave structure in the sample produced by a transmitted Gaussian beam to achieve accurate, low-noise measurement of the complex permittivity of the sample [e.g., J. A. Scales and M. Batzle, Appl. Phys. Lett. 88, 062906 (2006); R. N. Clarke and C. B. Rosenberg, J. Phys. E 15, 9 (1982); T. M. Hirovnen, P. Vainikainen, A. Lozowski, and A. V. Raisanen, IEEE Trans. Instrum. Meas. 45, 780 (1996)]. In effect the sample itself becomes a low-Q cavity. On the other hand, for optically thin samples (films of thickness much less than a wavelength) or extremely low loss samples (loss tangents below 10(-5)) the QO approach tends to break down due to loss of signal. In such a case it is useful to put the sample in a high-Q cavity and measure the perturbation of the cavity modes. Provided that the average mode frequency divided by the shift in mode frequency is less than the Q (quality factor) of the mode, then the perturbation should be resolvable. Cavity perturbation techniques are not new, but there are technological difficulties in working in the millimeter/submillimeter wave region. In this paper we will show applications of cavity perturbation to the dielectric characterization of semi-conductor thin films of the type used in the manufacture of photovoltaics in the 100 and 350 GHz range. We measured the complex optical constants of hot-wire chemical deposition grown 1-μm thick amorphous silicon (a-Si:H) film on borosilicate glass substrate. The real part of the refractive index and dielectric constant of the glass-substrate varies from frequency-independent to linearly frequency-dependent. We also see power-law behavior of the frequency-dependent optical conductivity from 316 GHz (9.48 cm(-1)) down to 104 GHz (3.12 cm(-1)).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, Yun; Wu, Xiaohan; Li, Qifan

Low magnetic loss ferrite composites consisting of Ba(CoTi){sub 1.2}Fe{sub 9.6}O{sub 19} and BiFeO{sub 3} (BFO) ferrite were investigated for permeability, permittivity, and high frequency losses at 10 MHz–1 GHz. The phase fraction of BiFeO{sub 3} was quantitatively analyzed by X-ray diffraction measurements. An effective medium approach was employed to predict the effective permeability and permittivity for the ferrite composites, which was found to be in good agreement with experimental data. The experiment demonstrated low magnetic losses (<0.128), modified by BFO phase fraction, while retaining high permeability (∼10.86) at 300 MHz. More importantly, the BFO phase resulted in a reduction of magnetic lossmore » by 32%, as BFO phase increased from 2.7 vol. % to 12.6 vol. %. The effect of BFO phase on magnetic and dielectric properties revealed great potential for use in the miniaturization of high efficiency antennas.« less

Terahertz absorption in graphite nanoplatelets/polylactic acid composites

NASA Astrophysics Data System (ADS)

Bychanok, D.; Angelova, P.; Paddubskaya, A.; Meisak, D.; Shashkova, L.; Demidenko, M.; Plyushch, A.; Ivanov, E.; Krastev, R.; Kotsilkova, R.; Ogrin, F. Y.; Kuzhir, P.

2018-04-01

The electromagnetic properties of composite materials based on poly(lactic) acid (PLA) filled with graphite nanoplatelets (GNP) were investigated in the microwave (26–37 GHz) and terahertz (0.2–1 THz) frequency ranges. The maximum of the imaginary part of the dielectric permittivity was observed close to 0.6 THz for composites with 1.5 and 3 wt.% of GNP. The experimental data of complex dielectric permittivity of GNP/PLA composites was modelled using the Maxwell-Garnett theory. The effects of fine dispersion, agglomeration, and percolation in GNP-based composites on its electromagnetic constitutive parameters, presence, and position of THz absorption peak are discussed on the basis of the modeling results and experimental data. The unique combination of conductive and geometrical parameters of GNP embedded into the PLA matrix below the percolation threshold allow us to obtain the THz-absorptive material, which may be effectively used as a 3D-printing filament.

Lattice dynamical and dielectric properties of L-amino acids

NASA Astrophysics Data System (ADS)

Tulip, P. R.; Clark, S. J.

2006-08-01

We present the results of ab initio calculations of the lattice dynamical and dielectric properties of the L-amino acids L-alanine, L-leucine, and L-isoleucine. Normal-mode frequencies and dielectric permittivity tensors are obtained using density-functional perturbation theory implemented within the plane-wave pseudopotential approximation. IR spectra are calculated and are used to analyze the effects of intermolecular interactions and zwitterionization upon the lattice dynamics. It is found that vibronic modes associated with the carboxy and amino functional groups undergo modification from their free-molecule values due to the presence of hydrogen bonds. The role of macroscopic electric fields set up by zone-center normal modes in the lattice dynamics is investigated by analysis of the Born effective charge. Calculated permittivity tensors are found to be greater than would be obtained by a naive use of the isolated molecular values, indicating the role of intermolecular interactions in increasing molecular polarizability.

Effect of meter-scale heterogeneities inside 67P nucleus on CONSERT data

NASA Astrophysics Data System (ADS)

Ciarletti, Valérie; Lasue, Jérémie; Lemonnier, Florentin; Kofman, Wlodek; Levasseur-Regourd, Anny-Chantal; Herique, Alain; Guiffaut, Christophe

2016-10-01

Since their arrival at comet 67P in August 2014, a number of instruments onboard Rosetta's main spacecraft and Philae lander have been observing the surface of the nucleus and revealed details of amazing surficial structures (hundreds of meters deep pits and cliffs, surface roughness of the order of a couple of meters in size, non-continuous apparent layers on both lobes of the comet). After two years of observations, the activity of the comet has also been better constrained, while the origin of sporadic jet activities remains debated. This surficial information is complemented by relevant measurements assessing the nucleus internal structure that have been collected by the CONSERT (Comet Nucleus Sounding Experiment by Radiowave Transmission) experiment in order to constrain the nucleus formation and evolution.The CONSERT experiment is a bistatic radar with receivers and transmitters on-board both Rosetta's main spacecraft and the Philae lander. The instrument transmits electromagnetic waves at 90 MHz (10 MHz bandwidth) between Philae and Rosetta. The signal propagated through the small lobe of 67P over distances ranging from approximately 200 to 800 meters depending on the spacecraft location and probed a maximum depth of about one hundred meters in the vicinity of the final landing site Abydos. The CONSERT data have been used to obtain an estimate of the permittivity mean value. Thanks to the 10 MHz frequency bandwidth of the signal used by the instrument, a spatial resolution around 10m is obtained inside the sounded volume of the nucleus.In this work, we analyze the effect of internal heterogeneities of 67P on the CONSERT data by simulating the propagation of the signal through a fractal model of the comet interior. We considered for the simulations a range of realistic permittivity values and characteristic sizes of the material heterogeneities. The different parameters values used have an impact on the width of the signal propagating through the modeled nucleus. Comparison with the values measured by CONSERT will allow us to determine the possible permittivity variations and heterogeneities size compatible with 67P internal structure.

Modelling Discharge Inception in Thunderstorms

NASA Astrophysics Data System (ADS)

Rutjes, C.; Dubinova, A.; Ebert, U.; Buitink, S.; Scholten, O.; Trinh, G. T. N.

2014-12-01

The electric fields in thunderstorms can exceed the breakdown value locally near hydrometeors. But are fields high enough and the regions large enough to initiate a streamer discharge? And where would a sufficient density of free electrons come from to start the discharge in the humid air that rapidly binds electrons in water-clusters? To analyse these questions, we investigate the interaction of extensive air showers (created by high energy cosmic particles) with the hydrometeors in a thunderstorm. The extensive air showers are modelled in full detail with CORSIKA (https://web.ikp.kit.edu/corsika/). As extensive air showers are occurring with a frequency that strongly depends on their size, proper stochastics are derived to cope with the large number of random variables in the system, such as: occurrence, primary energy, altitude of first interaction and inclination. These variables are important factors that determine the extremes of the high energy particle flux passing through a hydrometeor at a given altitude. In addition, the interaction of the high energy particle flux with the hydrometeor is modelled with EGS5 (http://rcwww.kek.jp/research/egs/egs5.html). Finally the streamer initiation and evolution is modelled by our 2.5D streamer fluid code that now can include dielectric bodies; here we used the frequency dependent dielectric permittivity of ice, accounting for the fact that ice can not polarise instantaneously.

A Novel Approach for Using Dielectric Spectroscopy to Predict Viable Cell Volume (VCV) in Early Process Development

PubMed Central

Downey, Brandon J; Graham, Lisa J; Breit, Jeffrey F; Glutting, Nathaniel K

2014-01-01

Online monitoring of viable cell volume (VCV) is essential to the development, monitoring, and control of bioprocesses. The commercial availability of steam-sterilizable dielectric-spectroscopy probes has enabled successful adoption of this technology as a key noninvasive method to measure VCV for cell-culture processes. Technological challenges still exist, however. For some cell lines, the technique's accuracy in predicting the VCV from probe-permittivity measurements declines as the viability of the cell culture decreases. To investigate the cause of this decrease in accuracy, divergences in predicted vs. actual VCV measurements were directly related to the shape of dielectric frequency scans collected during a cell culture. The changes in the shape of the beta dispersion, which are associated with changes in cell state, are quantified by applying a novel “area ratio” (AR) metric to frequency-scanning data from the dielectric-spectroscopy probes. The AR metric is then used to relate the shape of the beta dispersion to single-frequency permittivity measurements to accurately predict the offline VCV throughout an entire fed-batch run, regardless of cell state. This work demonstrates the possible feasibility of quantifying the shape of the beta dispersion, determined from frequency-scanning data, for enhanced measurement of VCV in mammalian cell cultures by applying a novel shape-characterization technique. In addition, this work demonstrates the utility of using changes in the shape of the beta dispersion to quantify cell health. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 30:479–487, 2014 PMID:24851255

A unified inversion scheme to process multifrequency measurements of various dispersive electromagnetic properties

NASA Astrophysics Data System (ADS)

Han, Y.; Misra, S.

2018-04-01

Multi-frequency measurement of a dispersive electromagnetic (EM) property, such as electrical conductivity, dielectric permittivity, or magnetic permeability, is commonly analyzed for purposes of material characterization. Such an analysis requires inversion of the multi-frequency measurement based on a specific relaxation model, such as Cole-Cole model or Pelton's model. We develop a unified inversion scheme that can be coupled to various type of relaxation models to independently process multi-frequency measurement of varied EM properties for purposes of improved EM-based geomaterial characterization. The proposed inversion scheme is firstly tested in few synthetic cases in which different relaxation models are coupled into the inversion scheme and then applied to multi-frequency complex conductivity, complex resistivity, complex permittivity, and complex impedance measurements. The method estimates up to seven relaxation-model parameters exhibiting convergence and accuracy for random initializations of the relaxation-model parameters within up to 3-orders of magnitude variation around the true parameter values. The proposed inversion method implements a bounded Levenberg algorithm with tuning initial values of damping parameter and its iterative adjustment factor, which are fixed in all the cases shown in this paper and irrespective of the type of measured EM property and the type of relaxation model. Notably, jump-out step and jump-back-in step are implemented as automated methods in the inversion scheme to prevent the inversion from getting trapped around local minima and to honor physical bounds of model parameters. The proposed inversion scheme can be easily used to process various types of EM measurements without major changes to the inversion scheme.

Scaling of terahertz conductivity at the metal-insulator transition in doped manganites

NASA Astrophysics Data System (ADS)

Pimenov, A.; Biberacher, M.; Ivannikov, D.; Loidl, A.; Mukhin, A. A.; Goncharov, Yu. G.; Balbashov, A. M.

2006-06-01

Magnetic field and temperature dependence of the terahertz conductivity and permittivity of the colossal magnetoresistance manganite Pr0.65Ca0.28Sr0.07MnO3 (PCSMO) is investigated approaching the metal-to-insulator transition (MIT) from the insulating side. In the charge-ordered state of PCSMO both conductivity and dielectric permittivity increase as a function of magnetic field and temperature. Universal scaling relationships Δɛ∝Δσ are observed in a broad range of temperatures and magnetic fields. Similar scaling is also seen in La1-xSrxMnO3 for different doping levels. The observed proportionality points towards the importance of pure ac-conductivity and phononic energy scale at MIT in manganites.

Dielectric relaxation and piezoelectric coupling in the mixed proton-glass crystal K[sub 0. 61](NH[sub 4])[sub 0. 39]H[sub 2]PO[sub 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tu, C.; Schmidt, V.H.; Saleh, A.A.

1993-11-01

Measurements of the dielectric permittivities in the mixed proton-glass crystal K[sub 0.61](NH[sub 4])[sub 0.39]H[sub 2]PO[sub 4] are reported from 20 Hz to 200.8 MHz and for fields along both the [ital a] and [ital c] axes. Between 14 and 50 K, the [ital c]-axis permittivity outside the piezoelectric-resonance range shows a temperature-dependent spread in relaxation times but cannot be fit accurately with the Cole-Cole formula. Strong piezoelectric resonance for a field along the [ital c] axis was observed in the region between 100 kHz and 10 MHz.

Influence of deposition conditions on electrical and mechanical properties of Sm2O3-doped CeO2 thin films prepared by EB-PVD (+IBAD) methods. Part 1: Effective relative permittivity

NASA Astrophysics Data System (ADS)

Hartmanová, Mária; Nádaždy, Vojtech; Kundracik, František; Mansilla, Catina

2013-03-01

Study is devoted to the effective relative permittivity ɛr of CeO2 + x. Sm2O3 thin films prepared by electron-beam physical vapour deposition and ionic beam-assisted deposition methods; ɛr was investigated by three independent ways from the bulk parallel capacitance Cp, impedance capacitance Cimp, and accumulation capacitance Cacc in dependence on the deposition conditions (deposition temperature, dopant amount x and Ar+ ion bombardment during the film deposition) used. Investigations were performed using impedance spectroscopy, capacitance-voltage and current-voltage characteristics as well as deep level transient spectroscopy. Results obtained are described and discussed.

Temperature evolution of the local order parameter in relaxor ferroelectrics (1 - x)PMN-xPZT

NASA Astrophysics Data System (ADS)

Gridnev, S. A.; Glazunov, A. A.; Tsotsorin, A. N.

2005-09-01

The temperature dependence of the local order parameter and relaxation time distribution function have been determined in (1 - x)PMN-xPZT ceramic samples via dielectric permittivity. Above the Burns temperature, the permittivity was found to follow the Currie-Weiss law, and with temperature decreasing the deviation was observed to increase. A local order parameter was calculated from the dielectric data using a modified Landau-Devonshire approach. These results are compared to the distribution function of relaxation times. It was found that a glasslike freezing of reorientable polar clusters occurs in the temperature range of diffuse relaxor transition. The evolution of the studied system to more ordered state arises from the increased PZT content.

Computational electromagnetic methods for transcranial magnetic stimulation

NASA Astrophysics Data System (ADS)

Gomez, Luis J.

Transcranial magnetic stimulation (TMS) is a noninvasive technique used both as a research tool for cognitive neuroscience and as a FDA approved treatment for depression. During TMS, coils positioned near the scalp generate electric fields and activate targeted brain regions. In this thesis, several computational electromagnetics methods that improve the analysis, design, and uncertainty quantification of TMS systems were developed. Analysis: A new fast direct technique for solving the large and sparse linear system of equations (LSEs) arising from the finite difference (FD) discretization of Maxwell's quasi-static equations was developed. Following a factorization step, the solver permits computation of TMS fields inside realistic brain models in seconds, allowing for patient-specific real-time usage during TMS. The solver is an alternative to iterative methods for solving FD LSEs, often requiring run-times of minutes. A new integral equation (IE) method for analyzing TMS fields was developed. The human head is highly-heterogeneous and characterized by high-relative permittivities (107). IE techniques for analyzing electromagnetic interactions with such media suffer from high-contrast and low-frequency breakdowns. The novel high-permittivity and low-frequency stable internally combined volume-surface IE method developed. The method not only applies to the analysis of high-permittivity objects, but it is also the first IE tool that is stable when analyzing highly-inhomogeneous negative permittivity plasmas. Design: TMS applications call for electric fields to be sharply focused on regions that lie deep inside the brain. Unfortunately, fields generated by present-day Figure-8 coils stimulate relatively large regions near the brain surface. An optimization method for designing single feed TMS coil-arrays capable of producing more localized and deeper stimulation was developed. Results show that the coil-arrays stimulate 2.4 cm into the head while stimulating 3.0 times less volume than Figure-8 coils. Uncertainty quantification (UQ): The location/volume/depth of the stimulated region during TMS is often strongly affected by variability in the position and orientation of TMS coils, as well as anatomical differences between patients. A surrogate model-assisted UQ framework was developed and used to statistically characterize TMS depression therapy. The framework identifies key parameters that strongly affect TMS fields, and partially explains variations in TMS treatment responses.

Terahertz metamaterials

DOEpatents

Peralta, Xomalin Guaiuli; Brener, Igal; O'Hara, John; Azad, Abul; Smirnova, Evgenya; Williams, John D.; Averitt, Richard D.

2014-08-12

Terahertz metamaterials comprise a periodic array of resonator elements disposed on a dielectric substrate or thin membrane, wherein the resonator elements have a structure that provides a tunable magnetic permeability or a tunable electric permittivity for incident electromagnetic radiation at a frequency greater than about 100 GHz and the periodic array has a lattice constant that is smaller than the wavelength of the incident electromagnetic radiation. Microfabricated metamaterials exhibit lower losses and can be assembled into three-dimensional structures that enable full coupling of incident electromagnetic terahertz radiation in two or three orthogonal directions. Furthermore, polarization sensitive and insensitive metamaterials at terahertz frequencies can enable new devices and applications.

Method of printed circuits and semiconductor substrates material parameters extraction using wideband reflection measurements

NASA Astrophysics Data System (ADS)

Savin, A. A.; Guba, V. G.; Ladur, A. A.; Bykova, O. N.

2018-05-01

This paper is dedicated to a new method of high frequency circuits material properties extraction based on the reflection measurements of a line shorted two or more times along its length. The line should be fabricated on the material under test. To achieve more precise calculation results, the proposed method uses processing in the time domain. The experimental results section shows obtained assessments for relative permittivity and dielectric loss tangent of the RO4350B hydrocarbon ceramic laminate. Measurements have been conducted over the frequency range up to 20 GHz.

Microwave Bandpass Filter Based on Mie-Resonance Extraordinary Transmission

PubMed Central

Pan, Xiaolong; Wang, Haiyan; Zhang, Dezhao; Xun, Shuang; Ouyang, Mengzhu; Fan, Wentao; Guo, Yunsheng; Wu, Ye; Huang, Shanguo; Bi, Ke; Lei, Ming

2016-01-01

Microwave bandpass filter structure has been designed and fabricated by filling the periodically metallic apertures with dielectric particles. The microwave cannot transmit through the metallic subwavelength apertures. By filling the metallic apertures with dielectric particles, a transmission passband with insertion loss 2 dB appears at the frequency of 10–12 GHz. Both simulated and experimental results show that the passband is induced by the Mie resonance of the dielectric particles. In addition, the passband frequency can be tuned by the size and the permittivity of the dielectric particles. This approach is suitable to fabricate the microwave bandpass filters. PMID:27992440

Column displacement experiments to evaluate electrical conductivity effects on electromagnetic soil water sensing

USDA-ARS?s Scientific Manuscript database

Bulk electrical conductivity (EC) in superactive soils has been shown to strongly influence electromagnetic sensing of permittivity. However, these effects are dependent on soil water content and temperature as well as the pore water conductivity. We carried out isothermal column displacement experi...

Electromagnetic pulse distortion in living tissue.

PubMed

Lepelaars, E S

1996-05-01

Insight into the distortion of electromagnetic (EM) signals in living tissue is important for optimising medical applications. To obtain this insight, field calculations have been carried out for a plane-stratified configuration of air, skin, fat, muscle and bone tissue. In this configuration, an EM field is generated by a prescribed pulsed current in a circular loop. Debye dispersion models have been developed for the description of the permittivity of the tissues. The field problem is solved analytically with the aid of a temporal Fourier transformation and a spatial Hankel transformation. The corresponding inverse transformations have been carried out numerically. To demonstrate the influences of stratification and dispersion separately, the EM fields in the stratified configuration, in a completely muscle-filled space and in vacuum are compared. Two different pulses have been considered; narrow and wide. It emerges that dispersion results in a retardation and an attenuation of the field. Stratification causes additional fluctuations of the time-dependent field. Furthermore, the conductivity of tissue at high frequencies is mainly determined by its water content. Tissues with high water content, like muscle and skin, exhibit higher conductivity at high frequencies than fat and bone. Muscle and skin tissue therefore behave as low-pass filters to EM signals.

Optical Time Reversal from Time-Dependent Epsilon-Near-Zero Media

NASA Astrophysics Data System (ADS)

Vezzoli, Stefano; Bruno, Vincenzo; DeVault, Clayton; Roger, Thomas; Shalaev, Vladimir M.; Boltasseva, Alexandra; Ferrera, Marcello; Clerici, Matteo; Dubietis, Audrius; Faccio, Daniele

2018-01-01

Materials with a spatially uniform but temporally varying optical response have applications ranging from magnetic field-free optical isolators to fundamental studies of quantum field theories. However, these effects typically become relevant only for time variations oscillating at optical frequencies, thus presenting a significant hurdle that severely limits the realization of such conditions. Here we present a thin-film material with a permittivity that pulsates (uniformly in space) at optical frequencies and realizes a time-reversing medium of the form originally proposed by Pendry [Science 322, 71 (2008), 10.1126/science.1162087]. We use an optically pumped, 500 nm thick film of epsilon-near-zero (ENZ) material based on Al-doped zinc oxide. An incident probe beam is both negatively refracted and time reversed through a reflected phase-conjugated beam. As a result of the high nonlinearity and the refractive index that is close to zero, the ENZ film leads to time reversed beams (simultaneous negative refraction and phase conjugation) with near-unit efficiency and greater-than-unit internal conversion efficiency. The ENZ platform therefore presents the time-reversal features required, e.g., for efficient subwavelength imaging, all-optical isolators and fundamental quantum field theory studies.

Electrode polarization and unusual magnetodielectric effect in a transformer oil-based magnetic nanofluid thin layer.

PubMed

Rajnak, Michal; Dolnik, Bystrik; Kurimsky, Juraj; Cimbala, Roman; Kopcansky, Peter; Timko, Milan

2017-01-07

In the present paper, we provide low-frequency dielectric spectra for a thin layer of a nanofluid based on transformer oil and iron oxide nanoparticles stabilized by oleic acid. The complex dielectric permittivity measured in the frequency range from 1 mHz to 200 kHz shows an obvious electrode polarization effect and a Debye-like dielectric relaxation process. Both effects stem from the presence of space charge in the oil due to impurity ions, and in the nanofluid represented predominantly by a residual surfactant and uncompensated particle surface charge. It is shown that the spectra, which were measured in the temperature range from 298 K to 358 K, can be well represented by a fitting function consisted of one Havriliak-Negami term and the Jonscher's power law. In the investigated magnetic nanofluid layer, we found that the onset of the electrode polarization is suppressed to lower frequencies by the application of an external magnetic field (300 mT). This phenomenon is explained by a slowed-down migration of the space charge due to the Lorentz force and by a hindering effect of the formed magnetic nanoparticle aggregates. Surprisingly, a moderate decrease in the whole permittivity spectrum was observed for both parallel and perpendicular orientations of the electric and magnetic fields. This is in contradiction with the usual magnetodielectric anisotropy effect. Based on our qualitative analysis, we discuss potential reasons accountable for the observed effect.

Intrinsic Enhancement of Dielectric Permittivity in (Nb + In) co-doped TiO2 single crystals.

PubMed

Kawarasaki, Masaru; Tanabe, Kenji; Terasaki, Ichiro; Fujii, Yasuhiro; Taniguchi, Hiroki

2017-07-13

The development of dielectric materials with colossal permittivity is important for the miniaturization of electronic devices and fabrication of high-density energy-storage devices. The electron-pinned defect-dipoles has been recently proposed to boost the permittivity of (Nb + In) co-doped TiO 2 to 10 5 . However, the follow-up studies suggest an extrinsic contribution to the colossal permittivity from thermally excited carriers. Herein, we demonstrate a marked enhancement in the permittivity of (Nb + In) co-doped TiO 2 single crystals at sufficiently low temperatures such that the thermally excited carriers are frozen out and exert no influence on the dielectric response. The results indicate that the permittivity attains quadruple of that for pure TiO 2 . This finding suggests that the electron-pinned defect-dipoles add an extra dielectric response to that of the TiO 2 host matrix. The results offer a novel approach for the development of functional dielectric materials with large permittivity by engineering complex defects into bulk materials.

Absorption Spectra of Gold Nanoparticle Suspensions

NASA Astrophysics Data System (ADS)

Anan'eva, M. V.; Nurmukhametov, D. R.; Zverev, A. S.; Nelyubina, N. V.; Zvekov, A. A.; Russakov, D. M.; Kalenskii, A. V.; Eremenko, A. N.

2018-02-01

Three gold nanoparticle suspensions are obtained, and mean radii in distributions - (6.1 ± 0.2), (11.9 ± 0.3), and (17.3 ± 0.7) nm - are determined by the transmission electron microscopy method. The optical absorption spectra of suspensions are obtained and studied. Calculation of spectral dependences of the absorption index of suspensions at values of the gold complex refractive index taken from the literature showed a significant deviation of experimental and calculated data in the region of 450-800 nm. Spectral dependences of the absorption of suspensions are simulated within the framework of the Mie-Drude theory taking into account the interband absorption in the form of an additional term in the imaginary part of the dielectric permittivity of the Gaussian type. It is shown that to quantify the spectral dependences in the region of the plasmon absorption band of nanoparticles, correction of the parameters of the interband absorption is necessary in addition to the increase of the relaxation parameter of the Drude theory. Spectral dependences of the dielectric permittivity of gold in nanodimensional state are refined from the solution of the inverse problem. The results of the present work are important for predicting the special features of operation of photonic devices and optical detonators based on gold nanoparticles.

Nonextensive statistics and skin depth of transverse wave in collisional plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hashemzadeh, M., E-mail: hashemzade@gmail.com

Skin depth of transverse wave in a collisional plasma is studied taking into account the nonextensive electron distribution function. Considering the kinetic theory for charge particles and using the Bhatnagar-Gross-Krook collision model, a generalized transverse dielectric permittivity is obtained. The transverse dispersion relation in different frequency ranges is investigated. Obtaining the imaginary part of the wave vector from the dispersion relation, the skin depth for these frequency ranges is also achieved. Profiles of the skin depth show that by increasing the q parameter, the penetration depth decreases. In addition, the skin depth increases by increasing the electron temperature. Finally, itmore » is found that in the high frequency range and high electron temperature, the penetration depth decreases by increasing the collision frequency. In contrast, by increasing the collision frequency in a highly collisional frequency range, the skin depth of transverse wave increases.« less

Design and validation of inert homemade explosive simulants for ground penetrating radar

NASA Astrophysics Data System (ADS)

VanderGaast, Brian W.; McFee, John E.; Russell, Kevin L.; Faust, Anthony A.

2015-05-01

The Canadian Armed Forces (CAF) identified a requirement for inert simulants to act as improvised, or homemade, explosives (IEs) when training on, or evaluating, ground penetrating radar (GPR) systems commonly used in the detection of buried landmines and improvised explosive devices (IEDs). In response, Defence R and D Canada (DRDC) initiated a project to develop IE simulant formulations using commonly available inert materials. These simulants are intended to approximate the expected GPR response of common ammonium nitrate-based IEs, in particular ammonium nitrate/fuel oil (ANFO) and ammonium nitrate/aluminum (ANAl). The complex permittivity over the range of electromagnetic frequencies relevant to standard GPR systems was measured for bulk quantities of these three IEs that had been fabricated at DRDC Suffield Research Centre. Following these measurements, published literature was examined to find benign materials with both a similar complex permittivity, as well as other physical properties deemed desirable - such as low-toxicity, thermal stability, and commercial availability - in order to select candidates for subsequent simulant formulation. Suitable simulant formulations were identified for ANFO, with resulting complex permittivities measured to be within acceptable limits of target values. These IE formulations will now undergo end-user trials with CAF operators in order to confirm their utility. Investigations into ANAl simulants continues. This progress report outlines the development program, simulant design, and current validation results.

Electron-pinned defect-dipoles for high-performance colossal permittivity materials

NASA Astrophysics Data System (ADS)

Hu, Wanbiao; Liu, Yun; Withers, Ray L.; Frankcombe, Terry J.; Norén, Lasse; Snashall, Amanda; Kitchin, Melanie; Smith, Paul; Gong, Bill; Chen, Hua; Schiemer, Jason; Brink, Frank; Wong-Leung, Jennifer

2013-09-01

The immense potential of colossal permittivity (CP) materials for use in modern microelectronics as well as for high-energy-density storage applications has propelled much recent research and development. Despite the discovery of several new classes of CP materials, the development of such materials with the required high performance is still a highly challenging task. Here, we propose a new electron-pinned, defect-dipole route to ideal CP behaviour, where hopping electrons are localized by designated lattice defect states to generate giant defect-dipoles and result in high-performance CP materials. We present a concrete example, (Nb+In) co-doped TiO2 rutile, that exhibits a largely temperature- and frequency-independent colossal permittivity (> 104) as well as a low dielectric loss (mostly < 0.05) over a very broad temperature range from 80 to 450 K. A systematic defect analysis coupled with density functional theory modelling suggests that ‘triangular’ In23+VO••Ti3+ and ‘diamond’ shaped Nb25+Ti3+ATi (A  =  Ti3+/In3+/Ti4+) defect complexes are strongly correlated, giving rise to large defect-dipole clusters containing highly localized electrons that are together responsible for the excellent CP properties observed in co-doped TiO2. This combined experimental and theoretical work opens up a promising feasible route to the systematic development of new high-performance CP materials via defect engineering.

Electron-pinned defect-dipoles for high-performance colossal permittivity materials.

PubMed

Hu, Wanbiao; Liu, Yun; Withers, Ray L; Frankcombe, Terry J; Norén, Lasse; Snashall, Amanda; Kitchin, Melanie; Smith, Paul; Gong, Bill; Chen, Hua; Schiemer, Jason; Brink, Frank; Wong-Leung, Jennifer

2013-09-01

The immense potential of colossal permittivity (CP) materials for use in modern microelectronics as well as for high-energy-density storage applications has propelled much recent research and development. Despite the discovery of several new classes of CP materials, the development of such materials with the required high performance is still a highly challenging task. Here, we propose a new electron-pinned, defect-dipole route to ideal CP behaviour, where hopping electrons are localized by designated lattice defect states to generate giant defect-dipoles and result in high-performance CP materials. We present a concrete example, (Nb+In) co-doped TiO₂ rutile, that exhibits a largely temperature- and frequency-independent colossal permittivity (> 10(4)) as well as a low dielectric loss (mostly < 0.05) over a very broad temperature range from 80 to 450 K. A systematic defect analysis coupled with density functional theory modelling suggests that 'triangular' In₂(3+)Vo(••)Ti(3+) and 'diamond' shaped Nb₂(5+)Ti(3+)A(Ti) (A = Ti(3+)/In(3+)/Ti(4+)) defect complexes are strongly correlated, giving rise to large defect-dipole clusters containing highly localized electrons that are together responsible for the excellent CP properties observed in co-doped TiO₂. This combined experimental and theoretical work opens up a promising feasible route to the systematic development of new high-performance CP materials via defect engineering.

An X-band waveguide measurement technique for the accurate characterization of materials with low dielectric loss permittivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allen, Kenneth W., E-mail: kenneth.allen@gtri.gatech.edu; Scott, Mark M.; Reid, David R.

In this work, we present a new X-band waveguide (WR90) measurement method that permits the broadband characterization of the complex permittivity for low dielectric loss tangent material specimens with improved accuracy. An electrically long polypropylene specimen that partially fills the cross-section is inserted into the waveguide and the transmitted scattering parameter (S{sub 21}) is measured. The extraction method relies on computational electromagnetic simulations, coupled with a genetic algorithm, to match the experimental S{sub 21} measurement. The sensitivity of the technique to sample length was explored by simulating specimen lengths from 2.54 to 15.24 cm, in 2.54 cm increments. Analysis ofmore » our simulated data predicts the technique will have the sensitivity to measure loss tangent values on the order of 10{sup −3} for materials such as polymers with relatively low real permittivity values. The ability to accurately characterize low-loss dielectric material specimens of polypropylene is demonstrated experimentally. The method was validated by excellent agreement with a free-space focused-beam system measurement of a polypropylene sheet. This technique provides the material measurement community with the ability to accurately extract material properties of low-loss material specimen over the entire X-band range. This technique could easily be extended to other frequency bands.« less

High temperature dielectrics and defect characteristic of (Nb, Mn, Zr) modified 0.4(Ba0.8Ca0.2)TiO3 - 0.6Bi(Mg0.5Ti0.5)O3 ceramics

NASA Astrophysics Data System (ADS)

Ren, Shaokai; Chen, Zhi; Yan, Tianxiang; Han, Feifei; Kuang, Xiaojun; Fang, Liang; Liu, Laijun

2018-07-01

Transition elements Nb, Mn and Zr were selected to substitute Ti of 0.4(Ba0.8Ca0.2)TiO3 -0.6Bi(Mg0.5Ti0.5)O3 (BCT-BMT) ceramic in order to extend its operation temperature and decrease its dielectric loss for the application of high-temperature capacitors. Nb and Mn play an opposite role on the defect compensation, decreasing and increasing the concentration of oxygen vacancies, respectively. The temperature of the maximum relative permittivity, Tm, decreases from 140 °C to 90 °C for the Nb and Zr modified BCT-BMT ceramics. The permittivity (εr) peak of the former exhibits a broad and stable relative permittivity ∼600 (±5% variation) from 50 °C to 520 °C with the dielectric loss ≤0.02 from 60 °C to 440 °C (1 kHz). The modified Curie-Weiss law indicates that the doping elements result in an enhancement of diffuse phase transition. Activation energies of relaxation frequency and conduction of the samples were characterized by the impedance spectroscopy. A clear relationship between the magnitude of activation energy and the concentration of oxygen vacancies was revealed.

High frequency electromagnetic impedance measurements for characterization, monitoring and verification efforts. 1998 annual progress report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, K.H.; Pellerin, L.; Becker, A.

1998-06-01

'Non-invasive, high-resolution imaging of the shallow subsurface is needed for delineation of buried waste, detection of unexploded ordinance, verification and monitoring of containment structures, and other environmental applications. Electromagnetic measurements at frequencies between 1 and 100 MHz are important for such applications, because the induction number of many targets is small due, and the ability to determine the dielectric permittivity in addition to electrical conductivity of the subsurface is possible. Earlier workers were successful in developing systems for detecting anomalous areas, but no quantifiable information was accurately determined. For high resolution imaging, accurate measurements are necessary so the field datamore » can be mapped into the space of the subsurface parameters. The authors are developing a non-invasive method for accurately imaging the electrical conductivity and dielectric permittivity of the shallow subsurface using the plane wave impedance approach, known as the magnetotelluric (MT) method at low frequencies. Electric and magnetic sensors are being tested in a known area against theoretical predictions, thereby insuring that the data collected with the high-frequency impedance (HFI) system will support high-resolution, multi-dimensional imaging techniques. The summary of the work to date is divided into three sections: equipment procurement, instrumentation, and theoretical developments. For most earth materials, the frequency range from 1 to 100 MHz encompasses a very difficult transition zone between the wave propagation of displacement currents and the diffusive behavior of conduction currents. Test equipment, such as signal generators and amplifiers, does not cover the entire range except at great expense. Hence the authors have divided the range of investigation into three sub-ranges: 1--10 MHz, 10--30 MHz, and 30--100 MHz. Results to date are in the lowest frequency range of 1--10 MHz. Even though conduction currents dominate in this range, as in traditional electromagnetic exploration methods, little work has been done by the geophysical community above 500 kHz.'« less

Magnetic and electromagnetic properties of composites of iron oxide and Co-B alloy prepared by chemical reduction

NASA Astrophysics Data System (ADS)

Li, XueAi; Han, XiJiang; Du, YunChen; Xu, Ping

2011-01-01

Magnetic and electromagnetic properties were investigated on the composites of iron oxide and Co-B alloy, which were prepared by a modified chemical reduction method. The composites are characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometry (VSM). The complex electromagnetic parameters (permittivity ɛr= ɛr'+j ɛr″ and permeability μr= μr'+j μr″) of paraffin mixed composite samples (paraffin:composites=1:1 in mass ratio) were measured in the frequency range 2-18 GHz by vector network analyzer. The measured real part ( ɛr') and imaginary part ( ɛr″) of the relative permittivity show two resonant peaks in the range of 2-18 GHz. The imaginary parts of relative permeability ( μr″) of all samples exhibited one broad resonant peak over the 2-8 GHz range. The μr″ of samples with higher molar ratio of Co to Fe (C and D) shows negative values within 13-18 GHz, which exhibit resonant and antiresonant permeabilities simultaneously. Calculation results indicated that the reflection loss values of the composites and paraffin wax mixtures are less than -10 dB with frequency width of about 6 GHz at the matching thickness.

Permittivity and temperature effects on rectification performance of self-switching diodes with different geometrical structures using two-dimensional device simulator

NASA Astrophysics Data System (ADS)

Zakaria, N. F.; Kasjoo, S. R.; Zailan, Z.; Isa, M. M.; Taking, S.; Arshad, M. K. M.

2017-12-01

Characterization on an InGaAs-based self-switching diode (SSD) using technology computer aided design (TCAD) aimed for optimizing the electrical rectification performance of the device is reported. The rectifying performance is mainly contributed by a parameter known as the curvature coefficient which is derived from the current-voltage (I-V) behavior of the device. As such, the curvature coefficient of SSD was analyzed in this work, not only by varying the device's geometrical structure, but also by implementing different dielectric relative permittivity of the device's trenches, ranging from 1.0 to 10. Furthermore, the simulations were performed under temperature range of 300-600 K. The results showed that increased temperature degraded the SSD's rectifying performance due to increased reverse current which can deteriorate the nonlinearity of the device's I-V characteristic. Moreover, an improved curvature coefficient can be achieved using silicon dioxide (∼3.9) as the SSD trenches. The cut-off frequency of SSD with zero-bias curvature coefficient of ∼30 V-1 attained in this work was approximately 80 GHz, operating at unbiased condition. The results obtained can assist the design of SSD to efficiently operate as rectifiers at microwave and terahertz frequencies.

Determining Electrical Properties Based on B1 Fields Measured in an MR Scanner Using a Multi-channel Transmit/Receive Coil: a General Approach

PubMed Central

Liu, Jiaen; Zhang, Xiaotong; Van de Moortele, Pierre-Francois; Schmitter, Sebastian

2013-01-01

Electrical Property Tomography (EPT) is a recently developed noninvasive technology to image the electrical conductivity and permittivity of biological tissues at Larmor frequency in Magnetic Resonance (MR) scanners. The absolute phase of the complex radio-frequency (RF) magnetic field (B1) is necessary for electrical property calculation. However, due to the lack of practical methods to directly measure the absolute B1 phases, current EPT techniques have been achieved with B1 phase estimation based on certain assumptions on object anatomy, coil structure and/or electromagnetic wave behavior associated with the main magnetic field, limiting EPT from a larger variety of applications. In this study, using a multi-channel transmit/receive coil, the framework of a new general approach for EPT has been introduced, which is independent on the assumptions utilized in previous studies. Using a human head model with realistic geometry, a series of computer simulations at 7T were conducted to evaluate the proposed method under different noise levels. Results showed that the proposed method can be used to reconstruct the conductivity and permittivity images with noticeable accuracy and stability. The feasibility of this approach was further evaluated in a phantom experiment at 7T. PMID:23743673

Self-consistent treatment of the local dielectric permittivity and electrostatic potential in solution for polarizable macromolecular force fields.

PubMed

Hassan, Sergio A

2012-08-21

A self-consistent method is presented for the calculation of the local dielectric permittivity and electrostatic potential generated by a solute of arbitrary shape and charge distribution in a polar and polarizable liquid. The structure and dynamics behavior of the liquid at the solute/liquid interface determine the spatial variations of the density and the dielectric response. Emphasis here is on the treatment of the interface. The method is an extension of conventional methods used in continuum protein electrostatics, and can be used to estimate changes in the static dielectric response of the liquid as it adapts to charge redistribution within the solute. This is most relevant in the context of polarizable force fields, during electron structure optimization in quantum chemical calculations, or upon charge transfer. The method is computationally efficient and well suited for code parallelization, and can be used for on-the-fly calculations of the local permittivity in dynamics simulations of systems with large and heterogeneous charge distributions, such as proteins, nucleic acids, and polyelectrolytes. Numerical calculation of the system free energy is discussed for the general case of a liquid with field-dependent dielectric response.

Self-consistent treatment of the local dielectric permittivity and electrostatic potential in solution for polarizable macromolecular force fields

NASA Astrophysics Data System (ADS)

Hassan, Sergio A.

2012-08-01

A self-consistent method is presented for the calculation of the local dielectric permittivity and electrostatic potential generated by a solute of arbitrary shape and charge distribution in a polar and polarizable liquid. The structure and dynamics behavior of the liquid at the solute/liquid interface determine the spatial variations of the density and the dielectric response. Emphasis here is on the treatment of the interface. The method is an extension of conventional methods used in continuum protein electrostatics, and can be used to estimate changes in the static dielectric response of the liquid as it adapts to charge redistribution within the solute. This is most relevant in the context of polarizable force fields, during electron structure optimization in quantum chemical calculations, or upon charge transfer. The method is computationally efficient and well suited for code parallelization, and can be used for on-the-fly calculations of the local permittivity in dynamics simulations of systems with large and heterogeneous charge distributions, such as proteins, nucleic acids, and polyelectrolytes. Numerical calculation of the system free energy is discussed for the general case of a liquid with field-dependent dielectric response.

Self-consistent treatment of the local dielectric permittivity and electrostatic potential in solution for polarizable macromolecular force fields

PubMed Central

Hassan, Sergio A.

2012-01-01

A self-consistent method is presented for the calculation of the local dielectric permittivity and electrostatic potential generated by a solute of arbitrary shape and charge distribution in a polar and polarizable liquid. The structure and dynamics behavior of the liquid at the solute/liquid interface determine the spatial variations of the density and the dielectric response. Emphasis here is on the treatment of the interface. The method is an extension of conventional methods used in continuum protein electrostatics, and can be used to estimate changes in the static dielectric response of the liquid as it adapts to charge redistribution within the solute. This is most relevant in the context of polarizable force fields, during electron structure optimization in quantum chemical calculations, or upon charge transfer. The method is computationally efficient and well suited for code parallelization, and can be used for on-the-fly calculations of the local permittivity in dynamics simulations of systems with large and heterogeneous charge distributions, such as proteins, nucleic acids, and polyelectrolytes. Numerical calculation of the system free energy is discussed for the general case of a liquid with field-dependent dielectric response. PMID:22920098

Epitaxial thin films

DOEpatents

Hunt, Andrew Tye; Deshpande, Girish; Lin, Wen-Yi; Jan, Tzyy-Jiuan

2006-04-25

Epitatial thin films for use as buffer layers for high temperature superconductors, electrolytes in solid oxide fuel cells (SOFC), gas separation membranes or dielectric material in electronic devices, are disclosed. By using CCVD, CACVD or any other suitable deposition process, epitaxial films having pore-free, ideal grain boundaries, and dense structure can be formed. Several different types of materials are disclosed for use as buffer layers in high temperature superconductors. In addition, the use of epitaxial thin films for electrolytes and electrode formation in SOFCs results in densification for pore-free and ideal gain boundary/interface microstructure. Gas separation membranes for the production of oxygen and hydrogen are also disclosed. These semipermeable membranes are formed by high-quality, dense, gas-tight, pinhole free sub-micro scale layers of mixed-conducting oxides on porous ceramic substrates. Epitaxial thin films as dielectric material in capacitors are also taught herein. Capacitors are utilized according to their capacitance values which are dependent on their physical structure and dielectric permittivity. The epitaxial thin films of the current invention form low-loss dielectric layers with extremely high permittivity. This high permittivity allows for the formation of capacitors that can have their capacitance adjusted by applying a DC bias between their electrodes.

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

NASA Astrophysics Data System (ADS)

Asami, Koji

2007-06-01

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

Structural, electrical properties and dielectric relaxations in Na+-ion-conducting solid polymer electrolyte.

PubMed

Arya, Anil; Sharma, A L

2018-04-25

In this paper, we have studied the structural, microstructural, electrical, dielectric properties and ion dynamics of a sodium-ion-conducting solid polymer electrolyte film comprising PEO 8 -NaPF 6 +  x wt. % succinonitrile. The structural and surface morphology properties have been investigated, respectively using x-ray diffraction and field emission scanning electron microscopy. The complex formation was examined using Fourier transform infrared spectroscopy, and the fraction of free anions/ion pairs obtained via deconvolution. The complex dielectric permittivity and loss tangent has been analyzed across the whole frequency window, and enables us to estimate the DC conductivity, dielectric strength, double layer capacitance and relaxation time. The presence of relaxing dipoles was determined by the addition of succinonitrile (wt./wt.) and the peak shift towards high frequency indicates the decrease of relaxation time. Further, relations among various relaxation times ([Formula: see text]) have been elucidated. The complex conductivity has been examined across the whole frequency window; it obeys the Universal Power Law, and displays strong dependency on succinonitrile content. The sigma representation ([Formula: see text]) was introduced in order to explore the ion dynamics by highlighting the dispersion region in the Cole-Cole plot ([Formula: see text]) in the lower frequency window; increase in the semicircle radius indicates a decrease of relaxation time. This observation is accompanied by enhancement in ionic conductivity and faster ion transport. A convincing, logical scheme to justify the experimental data has been proposed.

Effective cluster model of dielectric enhancement in metal-insulator composites

NASA Astrophysics Data System (ADS)

Doyle, W. T.; Jacobs, I. S.

1990-11-01

The electrical permittivity of a suspension of conducting spheres at high volume loading exhibits a large enhancement above the value predicted by the Clausius-Mossotti approximation. The permittivity enhancement is a dielectric anomaly accompanying a metallization transition that occurs when conducting particles are close packed. In disordered suspensions, close encounters can cause a permittivity enhancement at any volume loading. We attribute the permittivity enhancements typically observed in monodisperse disordered suspensions of conducting spheres to local metallized regions of high density produced by density fluctuations. We model a disordered suspension as a mixture, or mesosuspension, of isolated spheres and random close-packed spherical clusters of arbitrary size. Multipole interactions within the clusters are treated exactly. External interactions between clusters and isolated spheres are treated in the dipole approximation. Model permittivities are compared with Guillien's experimental permittivity measurements [Ann. Phys. (Paris) Ser. 11, 16, 205 (1941)] on liquid suspensions of Hg droplets in oil and with Turner's conductivity measurements [Chem. Eng. Sci. 31, 487 (1976)] on fluidized bed suspensions of ion-exchange resin beads in aqueous solution. New permittivity measurements at 10 GHz on solid suspensions of monodisperse metal spheres in polyurethane are presented and compared with the model permittivities. The effective spherical cluster model is in excellent agreement with the experiments over the entire accessible range of volume loading.

Electric-field induced phase transitions of dielectric colloids: Impact of multiparticle effects

NASA Astrophysics Data System (ADS)

Wood, Jeffery A.; Docoslis, Aristides

2012-05-01

The thermodynamic framework for predicting the electric-field induced fluid like-solid like phase transition of dielectric colloids developed by Khusid and Acrivos [Phys. Rev. E. 54, 5428 (1996)] is extended to examine the impact of multiscattering/multiparticle effects on the resulting phase diagrams. This was accomplished using effective permittivity models suitable both over the entire composition region for hard spheres (0≤c

Locally preserved α  →  β phase transition in natural radiation-damaged titanite (CaTiSiO5): evidence from laser-induced photoluminescence and dielectric measurements

NASA Astrophysics Data System (ADS)

Beirau, Tobias; Murawski, Dawid; Behrens, Harald; Salje, Ekhard K. H.; Groat, Lee A.; Kaden, Ronny; Pöllmann, Herbert; Bismayer, Ulrich

2018-01-01

In situ temperature-dependent laser-induced photoluminescence and dielectric measurements provide new evidence for the local occurrence of the α  →  β phase transition near 500 K in the preserved crystalline parts of natural radiation-damaged titanite (sample E2335 with ~24% amorphous fraction, containing Fe and Al impurities). Photoluminescence spectroscopic measurements show an anomaly in the vicinity of 500 K. The temperature-dependent evolution of the real part of the electrical conductivity (σ) and the real (ɛ‧) and the imaginary (ɛ″) part of the complex dielectric permittivity (ɛ *) of titanite have been measured at various AC frequencies (~1.2-96.8 kHz). Despite the masking and smearing effect of impurities and defects, the temperature-dependent behaviour of ɛ‧ and ɛ″ around the transition temperature of the investigated natural titanite E2335 shows a remarkable similarity to that of the synthetic end-member material (see Zhang et al (1995 Phys. Chem. Miner. 22 41-9)). This study indicates the suitability of photoluminescence and impedance spectroscopy for the detection of phase transitions, even in heavily disordered systems.

Artificial high effective permittivity medium in a SIW filled with metallic cylinders

NASA Astrophysics Data System (ADS)

Vicent, G.; Bronchalo, E.; Coves, A.; Torregrosa, G.

2018-02-01

A new topology of step-impedance band-pass filters in Substrate Integrated Waveguide (SIW) technology has been recently demonstrated in which low effective permittivity regions have been achieved by removing part of the substrate material and then shielding the perforated structure. Alternatively, in this work a new way to obtain an increased relative permittivity in the guiding region is proposed by periodically inserting metallic inclusions. This paper shows the results of a systematic study of the effective permittivity obtained in this way in a SIW in order to synthesize a higher effective permittivity, which can be used in the filter design.

Measuring the permittivity of the surface of the Churyumov-Gerasimenko nucleus: the PP-SESAME experiment on board the Philae/ROSETTA lander

NASA Astrophysics Data System (ADS)

Lethuillier, A.; Le Gall, A. A.; Hamelin, M.; Ciarletti, V.; Caujolle-Bert, S.; Schmidt, W.; Grard, R.

2014-12-01

Within Philae, the lander of the Rosetta spacecraft, the Permittivity Probe (PP) experiment as part of the Surface Electric Sounding and Acoustic Monitoring Experiment (SESAME) package was designed to measure the low frequency (Hz-kHz) electrical properties of the close subsurface of the nucleus.At frequencies below 10 kHz, the electrical signature of the matter is especially sensitive to the presence of water ice and its temperature. PP-SESAME will thus allow to determine the water ice content in the near-surface and to monitor its diurnal and orbital variations thus providing essential insight on the activity and evolution of the cometary nucleus.The PP-SESAME instrument is derived from the quadrupole array technique. A sinusoidal electrical current is sent into the ground through a first dipole, and the induced electrical voltage is measured with a second dipole. The complex permittivity of the material is inferred from the mutual impedance derived from the measurements. In practice, the influence of both the electronic circuit of the instrument and the conducting elements in its close environment must be accounted for in order to best estimate the dielectric constant and electric conductivity of the ground. To do this we have developed a method called the "capacity-influence matrix method".A replica of the instrument was recently built in LATMOS (France) and was tested in the frame of a field campaign in the giant ice cave system of Dachstein, Austria. In the caves, the ground is covered with a thick layer of ice, which temperature is rather constant throughout the year. This measurement campaign allowed us to test the "capacity influence matrix method" in a natural icy environment.The first measurements of the PP-SESAME/Philae experiment should be available in mid-November. In this paper we will present the "capacity-influence matrix method", the measurements and results from the Austrian field campaign and the preliminary analysis of the PP-SESAME/Philae data.

Optimal Electromagnetic (EM) Geophysical Techniques to Map the Concentration of Subsurface Ice and Adsorbed Water on Mars and the Moon

NASA Astrophysics Data System (ADS)

Stillman, D. E.; Grimm, R. E.

2013-12-01

Water ice is ubiquitous in our Solar System and is a probable target for planetary exploration. Mapping the lateral and vertical concentration of subsurface ice from or near the surface could determine the origin of lunar and martian ice and quantify a much-needed resource for human exploration. Determining subsurface ice concentration on Earth is not trivial and has been attempted previously with electrical resistivity tomography (ERT), ground penetrating radar (GPR), airborne EM (AEM), and nuclear magnetic resonance (NMR). These EM geophysical techniques do not actually detect ice, but rather the absence of unfrozen water. This causes a non-unique interpretation of frozen and dry subsurface sediments. This works well in the arctic because most locations are not dry. However, for planetary exploration, liquid water is exceedingly rare and subsurface mapping must discriminate between an ice-rich and a dry subsurface. Luckily, nature has provided a unique electrical signature of ice: its dielectric relaxation. The dielectric relaxation of ice creates a temperature and frequency dependence of the electrical properties and varies the relative dielectric permittivity from ~3.1 at radar frequencies to >100 at low frequencies. On Mars, sediments smaller than silt size can hold enough adsorbed unfrozen water to complicate the measurement. This is because the presence of absorbed water also creates frequency-dependent electrical properties. The dielectric relaxation of adsorbed water and ice can be separated as they have different shapes and frequency ranges as long as a spectrum spanning the two relaxations is measured. The volume concentration of ice and adsorbed water is a function of the strength of their relaxations. Therefore, we suggest that capacitively-coupled dielectric spectroscopy (a.k.a. spectral induced polarization or complex resistivity) can detect the concentration of both ice and adsorbed water in the subsurface. To prove this concept we have collected dielectric spectroscopy at the Cold Regions Research and Engineering Laboratory (CRREL) permafrost tunnel in Fox, AK. We were able to detect the ice relaxation in the subsurface despite the considerable amount of subsurface unfrozen water due to the presence of montmorillonite clay and much warmer temperatures than Mars or permanently shadowed regions of the Moon. While dielectric spectroscopy can be used to determine ice and adsorbed water content it does not possess the high resolution mapping capability of a GPR. Moreover, GPR cannot detect subsurface ice content in ice-sediment mixtures as evidenced in the interpretation of the Medusae Fossae Formation. Orbital radar surveys show this unit has a low attenuation and a dielectric permittivity near 4. This allows the formation to be interpreted as ice-rich or a dry high-porosity volcanic tuff unit. Therefore, combining GPR and dielectric spectroscopy will enable high-resolution structural and volatile mapping of the subsurface. Furthermore, the addition of neutron spectroscopy would add total hydrogen abundance in the top meter. This could lead to the determination of how much hydrogen resides in ice, adsorbed water, and minerals.

Temperature- and frequency-dependent dielectric behaviors of insulator/semiconductor (Al2O3/ZnO) nanolaminates with various ZnO thicknesses

NASA Astrophysics Data System (ADS)

Li, Jin; Bi, Xiaofang

2016-07-01

Al2O3/ZnO nanolaminates (NLs) with various ZnO sublayer thicknesses were prepared by atomic layer deposition. The Al2O3 sublayers are characterized as amorphous and the ZnO sublayers have an oriented polycrystalline structure. As the ZnO thickness decreases to a certain value, each NL exhibits a critical temperature at which its dielectric constant starts to rise quickly. Moreover, this temperature increases as the ZnO thickness is decreased further. On the other hand, the permittivity demonstrates a large value of several hundred at a frequency  ⩽1000 Hz, followed by a steplike decrease at a higher frequency. The change in the cut-off frequency with ZnO thickness is characterized by a hook function. It is revealed that the Coulomb confinement effect becomes predominant in the dielectric behaviors of the NLs with very thin ZnO. As the ZnO thickness decreases to about the same as or even smaller than the Bohr radius of ZnO, a great change in the carrier concentration and effective mass of ZnO is induced, which is shown to be responsible for the peculiar dielectric behaviors of Al2O3/ZnO with very thin ZnO. These findings provide insight into the prevailing mechanisms to optimize the dielectric properties of semiconductor/insulator laminates with nanoscale sublayer thickness.

Enhancement of the dielectric permittivity of (Nb1/2In1/2)0.02Ti0.98O2 single crystals at low temperatures due to (Nb + In) codoping

NASA Astrophysics Data System (ADS)

Taniguchi, Hiroki; Ando, Kako; Terasaki, Ichiro

2017-10-01

Dielectric measurements are performed on (Nb1/2In1/2)0.02Ti0.98O2 (NITO-2.0) single crystals grown by a floating zone method to address the nature of the colossal permittivity recently reported in (Nb + In) co-doped TiO2 ceramics. The colossal permittivity of the order of 105, which is also observed in the NITO-2.0 single crystals, disappears in the lowest temperature region, indicating an extrinsic contribution from thermally excited carriers to the colossal permittivity. Even at low temperatures where the thermally excited carriers are expected to be frozen out, a high permittivity of the order of 103 remains. This finding suggests that an intrinsic contribution from electron-pinned defect dipoles boosts the dielectric permittivity of TiO2.

An approach to the interpretation of Cole-Davidson and Cole-Cole dielectric functions

NASA Astrophysics Data System (ADS)

Iglesias, T. P.; Vilão, G.; Reis, João Carlos R.

2017-08-01

Assuming that a dielectric sample can be described by Debye's model at each frequency, a method based on Cole's treatment is proposed for the direct estimation at experimental frequencies of relaxation times and the corresponding static and infinite-frequency permittivities. These quantities and the link between dielectric strength and mean molecular dipole moment at each frequency could be useful to analyze dielectric relaxation processes. The method is applied to samples that follow a Cole-Cole or a Cole-Davidson dielectric function. A physical interpretation of these dielectric functions is proposed. The behavior of relaxation time with frequency can be distinguished between the two dielectric functions. The proposed method can also be applied to samples following a Navriliak-Negami or any other dielectric function. The dielectric relaxation of a nanofluid consisting of graphene nanoparticles dispersed in the oil squalane is reported and discussed within the novel framework.

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

PubMed

Yalçın, O; Coşkun, R; Okutan, M; Öztürk, M

2013-08-01

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

Microstructure and electrical properties of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shao, S. F.; Zhang, J. L.; Zheng, P.

2006-04-15

CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) ceramics are prepared by the conventional solid-state reaction method under various sintering temperatures from 1000 to 1120 deg. C at an interval of 10 deg. C. Microstructures and crystalline structures are examined by scanning electronic microscopy and x-ray diffraction, respectively. Dielectric properties and complex impedances are investigated within the frequency range of 40 Hz-110 MHz over the temperature region from room temperature to 350 deg. C. It has been disclosed that the microstructures can be categorized into three different types: type A (with the small but uniform grain sizes), type B (with the bimodal distributionmore » of grain sizes) and type C (with the large and uniform grain sizes), respectively. The largeness of low-frequency dielectric permittivity at room temperature is closely related to the microstructure. Ceramics with different types of microstructures show the diverse temperature-dependent behaviors of electrical properties. However, the existence of some common characteristics is also found among them. For all of the ceramics, a Debye-type relaxation emerges in the frequency range of 100 Hz-100 kHz at high measuring temperatures, which has the larger dielectric dispersion strength than the one known in the frequency range above 100 kHz. Thus, the high-temperature dielectric dispersion exhibits a large low-frequency response and two Debye-type relaxations. Furthermore, all of the ceramics show three semicircles in the complex impedance plane. These semicircles are considered to represent individually different electrical mechanisms, among which the one in the low-frequency range arises most probably from the contribution of the domain boundaries, and the other two are ascribed to the contributions of the domains and the grain boundaries, respectively.« less

Fractal-Inspired Subwavelength Geometric Inclusions for Improvement of High-Frequency Electromagnetic Devices

NASA Astrophysics Data System (ADS)

Smith, Kathryn Leigh

This dissertation presents research results demonstrating the efficacy of fractal-inspired subwavelength geometric inclusions for improvement of high-frequency electromagnetic devices. It begins with a review of the open literature in the area of fractal applications in antennas and metamaterials. This is followed by a detailed discussion of three high-frequency electromagnetic devices that demonstrate performance improvement through incorporation of subwavelength geometric design elements. The first of these devices is a spherical spiral metamaterial unit cell that was developed as a three-dimensional fractal expansion of the traditional split ring resonator, and is shown to be capable of producing broadband negative permeability, negative permittivity, or both, depending solely on the orientation of the unit cells with respect to the incident electric field. The second device is a ringed rectangular patch antenna that has four resonant frequencies. All four of these operative frequencies are shown to produce similar radiation patterns, which also closely match the pattern of a traditional patch antenna. Several minor geometric modifications of the basic shape of the device are also presented, and are shown to enable modification of the number of resonances, as well as tuning of frequencies of resonance. The third and final topic is a modified horn antenna that incorporates a spiral metamaterial as a phase-shifting device in order to achieve circularly polarized radiation. The handedness of the radiated wave is shown to be tunable through simple reorientation of the loading unit cells. In each of these cases, electrically-small geometric modification of existing device geometries is shown to greatly affect performance, either by increasing bandwidth, by inducing multiband behavior, or by enabling exotic radiation characteristics.

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

PubMed

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

2015-11-18

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yiyi; Wang, Junli; Qi, Shengli

In this report, a series of composite films consisting of polyimide as the matrix and multi-wall carbon nanotubes as the filler (PI/MWCNTs) were prepared in a water-based method with the use of triethylamine. Their dielectric properties were tested under frequency of between 100 Hz and 10 MHz, and it was revealed that the permittivity value behaved interestingly around the percolation threshold (8.01% in volume). The water-based method ensured that fillers had high dispersibility in the matrix before percolation, which led to a relatively high dielectric constant (284.28). However, the overlapping caused by excess MWCNTs created pathways for electrons inside the matrix, turningmore » the permittivity to negative. The former phenomenon was highly congruent with the percolation power law, while the latter could be explained by the Drude Model. AC conductivity was measured for more supportive information. Additionally, scanning electron microscopy and transmission electron microscopy were employed to record MWCNTs' microscopic distribution and morphology at the percolation threshold.« less

Recovery of permittivity and depth from near-field data as a step toward infrared nanotomography.

PubMed

Govyadinov, Alexander A; Mastel, Stefan; Golmar, Federico; Chuvilin, Andrey; Carney, P Scott; Hillenbrand, Rainer

2014-07-22

The increasing complexity of composite materials structured on the nanometer scale requires highly sensitive analytical tools for nanoscale chemical identification, ideally in three dimensions. While infrared near-field microscopy provides high chemical sensitivity and nanoscopic spatial resolution in two dimensions, the quantitative extraction of material properties of three-dimensionally structured samples has not been achieved yet. Here we introduce a method to perform rapid recovery of the thickness and permittivity of simple 3D structures (such as thin films and nanostructures) from near-field measurements, and provide its first experimental demonstration. This is accomplished via a novel nonlinear invertible model of the imaging process, taking advantage of the near-field data recorded at multiple harmonics of the oscillation frequency of the near-field probe. Our work enables quantitative nanoscale-resolved optical studies of thin films, coatings, and functionalization layers, as well as the structural analysis of multiphase materials, among others. It represents a major step toward the further goal of near-field nanotomography.

Research Update: Polyimide/CaCu3Ti4O12 nanofiber functional hybrid films with improved dielectric properties

NASA Astrophysics Data System (ADS)

Yang, Yang; Wang, Ziyu; Ding, Yi; Lu, Zhihong; Sun, Haoliang; Li, Ya; Wei, Jianhong; Xiong, Rui; Shi, Jing; Liu, Zhengyou; Lei, Qingquan

2013-11-01

This work reports the excellent dielectric properties of polyimide (PI) embedded with CaCu3Ti4O12 (CCTO) nanofibers. The dielectric behaviors were investigated over a frequency of 100 Hz-1 MHz. It is shown that embedding CCTO nanofibers with high aspect ratio (67) is an effective means to enhance the dielectric permittivity and reduce the percolation threshold. The dielectric permittivity of PI/CCTO nanofiber composites is 85 with 1.5 vol.% loading of filler, also the dielectric loss is only 0.015 at 100 Hz. Monte Carlo simulation was used to investigate the percolation threshold of CCTO nanofibers reinforced polyimide matrix by using excluded volume theory and soft, hard-core models. The results are in good agreement with the percolation theory and the hard-core model can well explain the percolation phenomena in PI/CCTO nanofiber composites. The dielectric properties of the composites will meet the practical requirements for the application in high dielectric constant capacitors and high energy density materials.

Experimental Verification of Guided-Wave Lumped Circuits Using Waveguide Metamaterials

NASA Astrophysics Data System (ADS)

Li, Yue; Zhang, Zhijun

2018-04-01

Through the construction and characterization in microwave frequencies, we experimentally demonstrate our recently developed theory of waveguide lumped circuits, i.e., waveguide metatronics [Sci. Adv. 2, e1501790 (2016), 10.1126/sciadv.1501790], as a method to design subwavelength-scaled analog circuits. In the paradigm of waveguide metatronics, numbers of lumped inductors and capacitors are easily integrated functionally inside the waveguide, which is an irreplaceable transmission line in millimeter-wave and terahertz systems with the advantages of low radiation loss and low crosstalk. An example of multiple-ordered metatronic filters with layered structures is fabricated utilizing the technique of substrate integrated waveguides, which can be easily constructed by the printed-circuit-board process. The materials used in the construction are also typical microwave materials with positive permittivity, low loss, and negligible dispersion, imitating the plasmonic materials with negative permittivity in the optical domain. The results verify the theory of waveguide metatronics, which provides an efficient platform of functional lumped circuit design for guided-wave processing.

Autonomous Sensors for Measuring Continuously the Moisture and Salinity of a Porous Medium

PubMed Central

Chavanne, Xavier; Frangi, Jean-Pierre

2017-01-01

The article describes a new field sensor to monitor continuously in situ moisture and salinity of a porous medium via measurements of its dielectric permittivity, conductivity and temperature. It intends to overcome difficulties and biases encountered with sensors based on the same sensitivity principle. Permittivity and conductivity are determined simultaneously by a self-balanced bridge, which measures directly the admittance of sensor electrodes in medium. All electric biases are reduced and their residuals taken into account by a physical model of the instrument, calibrated against reference fluids. Geometry electrode is optimized to obtain a well representative sample of the medium. The sensor also permits acquiring a large amount of data at high frequency (six points every hour, and even more) and to access it rapidly, even in real time, owing to autonomy capabilities and wireless communication. Ongoing developments intend to simplify and standardize present sensors. Results of field trials of prototypes in different environments are presented. PMID:28492471

Microwave absorbing property of silicone rubber composites with added carbonyl iron particles and graphite platelet

NASA Astrophysics Data System (ADS)

Xu, Yonggang; Zhang, Deyuan; Cai, Jun; Yuan, Liming; Zhang, Wenqiang

2013-02-01

Silicone rubber composites filled with carbonyl iron particles (CIPs) and graphite platelet (GP) were prepared using non-coating or coating processes. The complex permittivity and permeability of the composites were measured using a vector network analyzer in the frequency range of 1-18 GHz and dc electric conductivity was measured by the standard four-point contact method. The results showed that CIPs/GP composites fabricated in the coating process had the highest permittivity and permeability due to the particle orientation and interactions between the two absorbents. The coating process resulted in a decreased effective eccentricity of the absorbents, and the dc conductivity increased according to Neelakanta's equations. The reflection loss (RL) value showed that the composites had an excellent absorbing property in the L-band, minimum -11.85 dB at 1.5 mm and -15.02 dB at 2 mm. Thus, GP could be an effective additive in preparing thin absorbing composites in the L-band.

Autonomous Sensors for Measuring Continuously the Moisture and Salinity of a Porous Medium.

PubMed

Chavanne, Xavier; Frangi, Jean-Pierre

2017-05-11

The article describes a new field sensor to monitor continuously in situ moisture and salinity of a porous medium via measurements of its dielectric permittivity, conductivity and temperature. It intends to overcome difficulties and biases encountered with sensors based on the same sensitivity principle. Permittivity and conductivity are determined simultaneously by a self-balanced bridge, which measures directly the admittance of sensor electrodes in medium. All electric biases are reduced and their residuals taken into account by a physical model of the instrument, calibrated against reference fluids. Geometry electrode is optimized to obtain a well representative sample of the medium. The sensor also permits acquiring a large amount of data at high frequency (six points every hour, and even more) and to access it rapidly, even in real time, owing to autonomy capabilities and wireless communication. Ongoing developments intend to simplify and standardize present sensors. Results of field trials of prototypes in different environments are presented.

Center for Dielectric Studies at the Pennsylvania State University,

DTIC Science & Technology

1983-05-01

microstructure. The permittivity shows a weak peak near 100K which also has clear relaxation character and closely duplicates the behavior of higA purity...departures from the expected Curie-Weiss made by Demurov and Venevtsev.1 both hysteresis loops in P(E) behavior . Clearly. from the frequency response and...dielectric measurements, an powderl had second phase KzTa.O,,; powder II was completely anomalous behavior was observed by inelastic neutron scattering

High permittivity induced by interaction between PI matrix and graphite oxide filler

NASA Astrophysics Data System (ADS)

Lai, Maobai; Kou, Siwang; Yu, Shuhui; Sun, Rong; Wong, Ching-Ping

2014-09-01

Functionalized graphite oxide was introduced to polyimide and a colossal permittivity was obtained in the derived GO/PI composites. At 1 kHz, the permittivity of the composite with 3 wt% GO loading was up to 7179. In comparison, the permittivities of rGO/PI with 3 wt% rGO loading and GO/ER with 3 wt% GO loading were only 14.41 and 26.64, respectively. By analyzing the molecular structure and chemical bonding of GO/PI composites, we proposed that interaction occurred between the GO fillers carrying functional groups and the PI matrix with a conjugate system, which accounts for the high permittivity of GO/PI composites.

Dipole interaction of the Quincke rotating particles.

PubMed

Dolinsky, Yu; Elperin, T

2012-02-01

We study the behavior of particles having a finite electric permittivity and conductivity in a weakly conducting fluid under the action of the external electric field. We consider the case when the strength of the external electric field is above the threshold, and particles rotate due to the Quincke effect. We determine the magnitude of the dipole interaction of the Quincke rotating particles and the shift of frequency of the Quincke rotation caused by the dipole interaction between the particles. It is demonstrated that depending on the mutual orientation of the vectors of angular velocities of particles, vector-directed along the straight line between the centers of the particles and the external electric field strength vector, particles can attract or repel each other. In contrast to the case of nonrotating particles when the magnitude of the dipole interaction increases with the increase of the strength of the external electric field, the magnitude of the dipole interaction of the Quincke rotating particles either does not change or decreases with the increase of the strength of the external electric field depending on the strength of the external electric field and electrodynamic parameters of the particles.

Dipole interaction of the Quincke rotating particles

NASA Astrophysics Data System (ADS)

Dolinsky, Yu.; Elperin, T.

2012-02-01

We study the behavior of particles having a finite electric permittivity and conductivity in a weakly conducting fluid under the action of the external electric field. We consider the case when the strength of the external electric field is above the threshold, and particles rotate due to the Quincke effect. We determine the magnitude of the dipole interaction of the Quincke rotating particles and the shift of frequency of the Quincke rotation caused by the dipole interaction between the particles. It is demonstrated that depending on the mutual orientation of the vectors of angular velocities of particles, vector-directed along the straight line between the centers of the particles and the external electric field strength vector, particles can attract or repel each other. In contrast to the case of nonrotating particles when the magnitude of the dipole interaction increases with the increase of the strength of the external electric field, the magnitude of the dipole interaction of the Quincke rotating particles either does not change or decreases with the increase of the strength of the external electric field depending on the strength of the external electric field and electrodynamic parameters of the particles.

Structure and dielectric properties of (Ba0.7Sr0.3)1- x Na x (Ti0.9Sn0.1)1- x Nb x O3 ceramics

NASA Astrophysics Data System (ADS)

Ghoudi, Hanen; Chkoundali, Souad; Aydi, Abdelhedi; Khirouni, Kamel

2017-11-01

(Ba0.7Sr0.3)1- x Na x (Ti0.9Sn0.1)1- x Nb x O3 ceramics with compositions x = 0.6, 0.7, 0.8 and 0.9 were synthesized using the solid-state reaction method. These ceramics were examined by X-ray diffraction and dielectric measurements over a broad temperature and frequency ranges. X-ray diffraction patterns revealed a single-perovskite phase crystallized in a cubic structure, for x < 0.8, and in tetragonal, for x ≥ 0.8, with Pm3m and P4mm spaces groups, respectively. Two types of behaviors, classical ferroelectric or relaxor, were observed depending on the x composition. It is noted that temperatures T C (the Curie temperature) or T m (the temperature of maximum permittivity) rise when x increases and the relaxor character grows more significantly when x composition decreases. To analyze the dielectric relaxation degree of relaxor, various models were considered. It was proven that an exponential function could well describe the temperature dependence of the static dielectric constant and relaxation time.

Dielectric and electrical study of PPy doped PVA-PVP films

NASA Astrophysics Data System (ADS)

Jha, Sushma; Tripathi, Deepti

2018-05-01

Dielectric parameters of free standing films of pure PVA (PolyvinylAlcohol) and PVA with varying concentrations of PVP(Polyvinylpyrrolidone) and Polypyrrole were prepared and studied in low frequency range (100Hz - 2MHz). The results show that dielectric constant, loss tangent and conductivity increase sharply on increasing the concentration of PVP above 50wt% in polymer matrix. PVA-PVP film with low concentration of PPy showed improvement in the values of complex permittivity, loss tangent and ac conductivity within the experimental frequency range. This eco - friendly polymeric material will be studied for its probable application for RFI/EMI shielding, biosensors, capacitors & insulation purposes.

Photon energy conversion by near-zero permittivity nonlinear materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luk, Ting S.; Sinclair, Michael B.; Campione, Salvatore

Efficient harmonic light generation can be achieved with ultrathin films by coupling an incident pump wave to an epsilon-near-zero (ENZ) mode of the thin film. As an example, efficient third harmonic generation from an indium tin oxide nanofilm (.lamda./42 thick) on a glass substrate for a pump wavelength of 1.4 .mu.m was demonstrated. A conversion efficiency of 3.3.times.10.sup.-6 was achieved by exploiting the field enhancement properties of the ENZ mode with an enhancement factor of 200. This nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.

Resonance transparency with low-loss in toroidal planar metamaterial

NASA Astrophysics Data System (ADS)

Xiang, Tianyu; Lei, Tao; Hu, Sen; Chen, Jiao; Huang, Xiaojun; Yang, Helin

2018-03-01

A compact planar construction composed of asymmetric split ring resonators was designed with a low-loss, high Q-factor resonance transparency at microwave frequency. The singularity property of the proposed metamaterial owing to the enhanced toroidal dipole T is demonstrated via numerical and experimental methods. The transmission peak can reach up to 0.91 and the loss is perfectly repressed, which can be testified by radiated power, H-field distributions, and the imaginary parts of effective permittivity and permeability. The designed planar metamaterial may have numerous potential applications at microwave, terahertz, and optical frequency, e.g., for ultrasensitive sensing, slow-light devices, lasing spacers, even invisible information transfer.

Electromagnetic reflection from multi-layered snow models

NASA Technical Reports Server (NTRS)

Linlor, W. I.; Jiracek, G. R.

1975-01-01

The remote sensing of snow-pack characteristics with surface installations or an airborne system could have important applications in water-resource management and flood prediction. To derive some insight into such applications, the electromagnetic response of multilayered snow models is analyzed in this paper. Normally incident plane waves at frequencies ranging from 1 MHz to 10 GHz are assumed, and amplitude reflection coefficients are calculated for models having various snow-layer combinations, including ice layers. Layers are defined by thickness, permittivity, and conductivity; the electrical parameters are constant or prescribed functions of frequency. To illustrate the effect of various layering combinations, results are given in the form of curves of amplitude reflection coefficients versus frequency for a variety of models. Under simplifying assumptions, the snow thickness and effective dielectric constant can be estimated from the variations of reflection coefficient as a function of frequency.

Tunable angle absorption of hyperbolic metamaterials based on plasma photonic crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiao, Zheng; Ning, Renxia, E-mail: nrxxiner@hsu.edu.cn; Xu, Yuan

2016-06-15

We present the design of a multilayer structure of hyperbolic metamaterials based on plasma photonic crystals which composed of two kinds of traditional dielectric and plasma. The relative permittivity of hyperbolic metamaterials has been studied at certain frequency range. The absorption and reflection of the multilayer period structure at normal and oblique incident have been investigated by the transfer matrix method. We discussed that the absorption is affected by the thickness of material and the electron collision frequency γ of the plasma. The results show that an absorption band at the low frequency can be obtained at normal incident anglemore » and another absorption band at the high frequency can be found at a large incident angle. The results may be applied by logical gate, stealth, tunable angle absorber, and large angle filter.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ctibor, Pavel; Kotlan, Jiri, E-mail: kotlan@ipp.cas.cz; Department of Electrotechnology, Faculty of Electrical Engineering, Czech Technical University in Prague, Technicka 2, Prague 6

Highlights: • Calcium titanate was sprayed by two different plasma spray systems. • Significant improvement of dielectric properties after annealing was observed. • Calcium titanate self-supporting parts can be fabricated by plasma spraying. - Abstract: This paper studies calcium titanate (CaTiO{sub 3}) dielectrics prepared by plasma spray technology. A water stabilized plasma gun (WSP) as well as a widely used gas stabilized plasma gun (GSP) were employed in this study to deposit three sample sets at different spray conditions. Prepared specimens were annealed in air at atmospheric pressure for 2 h at various temperatures from 530 to 1170 °C. X-raymore » diffraction (XRD), Raman spectroscopy and porosity measurements were used for sample characterization. Dielectric spectroscopy was applied to obtain relative permittivity, conductivity and loss factor frequency dependence. Band gap energy was estimated from reflectance measurements. The work is focused on the explanation of changes in microstructure and properties of a plasma sprayed deposit after thermal annealing. Obtained results show significant improvement of dielectric properties after thermal annealing.« less

Open-Ended Coaxial Dielectric Probe Effective Penetration Depth Determination.

PubMed

Meaney, Paul M; Gregory, Andrew P; Seppälä, Jan; Lahtinen, Tapani

2016-03-01

We have performed a series of experiments which demonstrate the effect of open-ended coaxial diameter on the depth of penetration. We used a two layer configuration of a liquid and movable cylindrical piece of either Teflon or acrylic. The technique accurately demonstrates the depth in a sample for which a given probe diameter provides a reasonable measure of the bulk dielectric properties for a heterogeneous volume. In addition we have developed a technique for determining the effective depth for a given probe diameter size. Using a set of simulations mimicking four 50 Ω coaxial cable diameters, we demonstrate that the penetration depth in both water and saline has a clear dependence on probe diameter but is remarkably uniform over frequency and with respect to the intervening liquid permittivity. Two different 50 Ω commercial probes were similarly tested and confirm these observations. This result has significant implications to a range of dielectric measurements, most notably in the area of tissue property studies.

Open-Ended Coaxial Dielectric Probe Effective Penetration Depth Determination

PubMed Central

Meaney, Paul M.; Gregory, Andrew P.; Seppälä, Jan; Lahtinen, Tapani

2016-01-01

We have performed a series of experiments which demonstrate the effect of open-ended coaxial diameter on the depth of penetration. We used a two layer configuration of a liquid and movable cylindrical piece of either Teflon or acrylic. The technique accurately demonstrates the depth in a sample for which a given probe diameter provides a reasonable measure of the bulk dielectric properties for a heterogeneous volume. In addition we have developed a technique for determining the effective depth for a given probe diameter size. Using a set of simulations mimicking four 50 Ω coaxial cable diameters, we demonstrate that the penetration depth in both water and saline has a clear dependence on probe diameter but is remarkably uniform over frequency and with respect to the intervening liquid permittivity. Two different 50 Ω commercial probes were similarly tested and confirm these observations. This result has significant implications to a range of dielectric measurements, most notably in the area of tissue property studies. PMID:27346890

Reversible Phase Transition with Ultralarge Dielectric Relaxation Behaviors in Succinimide Lithium(I) Hybrids.

PubMed

Tang, Yun-Zhi; Wang, Bin; Zhou, Hai-Tao; Chen, Shao-Peng; Tan, Yu-Hui; Wang, Chang-Feng; Yang, Chang-Shan; Wen, He-Rui

2018-02-05

Dielectric relaxations have widely applied on high permittivity capacitors, dielectric switches, ferroelectrics, pyroelectrics, and electrical insulating materials. However, few investigations of large dielectric relaxation behaviors on organic-inorganic hybrid materials have been documented before. Here we present a novel two-dimensional succinimide lithium(I) hybrid compound, [Li(PDD) 2 ClO 4 ] n , 1, (PDD = 2,5-pyrrolidinedione = succinimide) which shows reversible phase transition behavior in the vicinity of 228 K accompanied by an unusual symmetry breaking from I4 1 /amd to C2/c. X-ray single crystal diffractions analysis indicates the twist motion of pyrrolidine heterocycles, and order-disorder motion of ClO 4 - anions triggered the reversible phase transition. By means of an intuitive crystallographic model (rattling ion model), we further illustrated the mechanism of the interesting reversible phase transition. Particularly, 1 shows ultralarge dielectric relaxation behavior in the vicinity of the phase transition by its dielectric constant dependence on temperatures and frequencies as well as its Cole-Cole relation.

Effects of silicon nanowires (SiNWs) contents on the optical and dielectric properties of poly(3-hexylthiophene):SiNWs nanocomposites

NASA Astrophysics Data System (ADS)

Saidi, Hamza; Walid, Aloui; Bouazizi, Abdelaziz; Herrero, Beatriz Romero; Saidi, Faouzi

2017-08-01

In this study, we investigated the dependency of the optical and electrical proprieties of poly(3-hexylthiophene):silicon nanowires (P3HT:SiNWs) nanocomposites on the concentration of SiNWs based on photoluminescence (PL) and impedance spectroscopy. The PL spectra indicated the presence of charge transfer at low concentrations of SiNWs. The effects of the SiNWs contents on the loss mechanism were determined based on permittivity measurements, which were related to the distribution of the SiNWs contents on the polymer backbones, as well as being correlated with the PL and conductance results. The imaginary part of the impedance exhibited a high relaxation frequency attributable to Maxwell-Wagner polarization, where the extracted relaxation time was in the range of milliseconds. The Cole-Cole diagram had an excellent fit via the equivalent circuit, which incorporated the chemical capacitance Cμ, contact electrical resistance Rs, and recombination resistance Rp.

Dielectric relaxation and ac conductivity behavior of carboxyl functionalized multiwalled carbon nanotubes/poly (vinyl alcohol) composites

NASA Astrophysics Data System (ADS)

Amrin, Sayed; Deshpande, V. D.

2017-03-01

We study the dielectric relaxation and ac conductivity behavior of MWCNT-COOH/Polyvinyl alcohol nanocomposite films in the temperature (T) range 303-423 K and in the frequency (f) range 0.1 Hz-1 MHz. The dielectric constant increases with an increase in temperature and also with an increase in MWCNT-COOH loading into the polymer matrix, as a result of interfacial polarization. The permittivity data were found to fit well with the modified Cole-Cole equation. Temperature dependent values of the relaxation times, free charge carrier conductivity and space charge carrier conductivity were extracted from the equation. An observed increment in the ac conductivity for the nanocomposites was analysed by a Jonscher power law which suggests that the correlated barrier hopping is the dominant charge transport mechanism for the nanocomposite films. The electric modulus study revealed deviations from ideal Debye-type behavior which are explained by considering a generalized susceptibility function. XRD and DSC results show an increase in the degree of crystallinity.

Study of hopping type conduction from AC conductivity in multiferroic composite

NASA Astrophysics Data System (ADS)

Pandey, Rabichandra; Guha, Shampa; Pradhan, Lagen Kumar; Kumar, Sunil; Supriya, Sweety; Kar, Manoranjan

2018-05-01

0.5BiFe0.80Ti0.20O3-0.5Co0.5Ni0.5Fe2O4(BFTO-CNFO) multiferroic composite was prepared by planetary ball mill method. X-ray diffraction analysis confirms the formation of the compound with the simultaneous presence of spinel Co0.5Ni0.5Fe2O4 (CNFO) and perovskite BiFe0.80Ti0.20O3 (BFTO) phase. Temperature dependent dielectric permittivity and loss tangent were studied with a frequency range of 100Hz to 1MHz. AC conductivity study was performed to analyze the electrical conduction behaviour in the composite. Johnscher's power law was employed to the AC conductivity data to understand the hopping of localized charge carrier in the compound. The binding energy, minimum hopping distance and density of states of the charge carriers in the composite were evaluated from the AC conductivity data. Minimum hopping distance is found to be in order of Angstrom (Å).

Low temperature dielectric relaxation in ordinary perovskite ferroelectrics: enlightenment from high-energy x-ray diffraction

DOE PAGES

Ochoa, D. A.; Levit, R.; Fancher, C. M.; ...

2017-04-05

We report that ordinary ferroelectrics exhibit a second order phase transition that is characterized by a sharp peak in the dielectric permittivity at a frequency-independent temperature. Furthermore, these materials show a low temperature dielectric relaxation that appears to be a common behavior of perovskite systems. Tetragonal lead zirconate titanate is used here as a model system in order to explore the origin of such an anomaly, since there is no consensus about the physical phenomenon involved in it. Crystallographic and domain structure studies are performed from temperature dependent synchrotron x-ray diffraction measurement. Results indicate that the dielectric relaxation cannot bemore » associated with crystallographic or domain configuration changes. The relaxation process is then parameterized by using the Vogel–Fulcher–Tammann phenomenological equation. Finally, results allow us to hypothesize that the observed phenomenon is due to changes in the dynamic behavior of the ferroelectric domains related to the fluctuation of the local polarization.« less

Imaging of voids by means of a physical-optics-based shape-reconstruction algorithm.

PubMed

Liseno, Angelo; Pierri, Rocco

2004-06-01

We analyze the performance of a shape-reconstruction algorithm for the retrieval of voids starting from the electromagnetic scattered field. Such an algorithm exploits the physical optics (PO) approximation to obtain a linear unknown-data relationship and performs inversions by means of the singular-value-decomposition approach. In the case of voids, in addition to a geometrical optics reflection, the presence of the lateral wave phenomenon must be considered. We analyze the effect of the presence of lateral waves on the reconstructions. For the sake of shape reconstruction, we can regard the PO algorithm as one of assuming the electric and magnetic field on the illuminated side as constant in amplitude and linear in phase, as far as the dependence on the frequency is concerned. Therefore we analyze how much the lateral wave phenomenon impairs such an assumption, and we show inversions for both one single and two circular voids, for different values of the background permittivity.

Plug identification in drainage system using electromagnetic wave

NASA Astrophysics Data System (ADS)

Hijriani, Arifa; Utama, Aji Surya; Boas, Andrianus; Mukti, M. Ridho; Widodo

2017-07-01

The evaluation of drainage system's performance is an important thing to do to prevent flooding. Conventionally the Government evaluates the drainage system by opening one by one the lid of drainage and detects the plug manually. This method is not effective and efficient because this method need many people, much time and relatively expensive. The purpose of this paper is to identify plugs in drainage system in G St. at Bandung Institute of Technology by using electromagnetic wave. Ground Penetrating Radar (GPR) is one of geophysics method that using electromagnetic wave with high frequency. GPR is a non-destructive method with high resolution imaging for shallow depth (˜100m) and relatively cheap. We could identify the plug without opening the lid manually so that we could save much time. GPR's sensitivity is depends on resistivity, magnetic permeability, and permittivity of an object. The result of this research is we could identify the plug on the radargram that observed by a build-up amplitude anomaly.