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

International Nuclear Information System (INIS)

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

2010-01-01

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

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

International Nuclear Information System (INIS)

Misirlioglu, I B; Yildiz, M

2013-01-01

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

Dielectric response and ac conductivity analysis of hafnium oxide nanopowder

International Nuclear Information System (INIS)

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

2012-01-01

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

Reduced dielectric response in spatially varying electric fields

DEFF Research Database (Denmark)

Hansen, Jesper Schmidt

2015-01-01

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

Dielectric function and its predicted effect on localized plasmon resonances of equiatomic Au–Cu

International Nuclear Information System (INIS)

De Silva, K S B; Gentle, A; Arnold, M; Cortie, M B; Keast, V J

2015-01-01

Equiatomic (Au,Cu) solid solution orders below 658 K to form a tetragonal AuCu (I) phase with significant changes in physical properties and the crystal structure. The effect of ordering on the dielectric function of the material is controversial however, with inconsistent results reported in the literature. Since the nature of any localized surface plasmon resonance (LSPR) in the nanostructures is very sensitive to the dielectric function, this uncertainty hinders the use of AuCu in plasmonic devices or structures. Therefore, we re-examine the question using a combination of measurements and computations. We find that no significant change in the dielectric function occurs when this material becomes ordered, at least over the range of photon energies relevant to LSPRs. The likely properties of LSPRs in plasmonic devices made of AuCu are analyzed. Use of the alloy offers some advantages over pure Cu, however pure Au would still be the superior option in most situations. (paper)

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

Directory of Open Access Journals (Sweden)

Gladush M.G.

2017-01-01

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

Analytical solutions of nonlocal Poisson dielectric models with multiple point charges inside a dielectric sphere

Science.gov (United States)

Xie, Dexuan; Volkmer, Hans W.; Ying, Jinyong

2016-04-01

The nonlocal dielectric approach has led to new models and solvers for predicting electrostatics of proteins (or other biomolecules), but how to validate and compare them remains a challenge. To promote such a study, in this paper, two typical nonlocal dielectric models are revisited. Their analytical solutions are then found in the expressions of simple series for a dielectric sphere containing any number of point charges. As a special case, the analytical solution of the corresponding Poisson dielectric model is also derived in simple series, which significantly improves the well known Kirkwood's double series expansion. Furthermore, a convolution of one nonlocal dielectric solution with a commonly used nonlocal kernel function is obtained, along with the reaction parts of these local and nonlocal solutions. To turn these new series solutions into a valuable research tool, they are programed as a free fortran software package, which can input point charge data directly from a protein data bank file. Consequently, different validation tests can be quickly done on different proteins. Finally, a test example for a protein with 488 atomic charges is reported to demonstrate the differences between the local and nonlocal models as well as the importance of using the reaction parts to develop local and nonlocal dielectric solvers.

Enhanced electric and magnetic response of a THz sub-wavelength fiber excited by a localized source

DEFF Research Database (Denmark)

Atakaramians, Shaghik; Stefani, Alessio; Shardivov, Ilya V.

2017-01-01

the magnetic response of the coupled system when excited with an electric dipole oriented along the circumference of the fiber. This result introduces a new platform for achieving enhanced magnetic response, which is the fundamental building block for metamaterial devices. Here we investigate experimentally......Recently we have shown that a nanofiber excited by a localized electric source can have enhanced electric and magnetic response depending of the relative orientation of the source and the fiber [1]. We have demonstrated that the dielectric nanofiber can suppress the electric response and enhance...

Positron annihilation response and broadband dielectric spectroscopy: salol.

Science.gov (United States)

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

2011-09-01

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

Light in complex dielectrics

NARCIS (Netherlands)

Schuurmans, F.J.P.

1999-01-01

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

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

Directory of Open Access Journals (Sweden)

A. Eršte

2016-03-01

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

Dielectric response and pyroelectric properties of lead-free ferroelectric Ba3(VO42

Directory of Open Access Journals (Sweden)

Biswajit Pati

2015-03-01

Full Text Available The current paper presents results of dielectric response, pyroelectric behavior and conductivity study of lead-free ferroelectric barium orthovanadate (Ba3(VO42 or Ba3V2O8 ceramic, for a wide range of temperature and frequency. An X-ray diffraction study suggests the formation of a single-phase compound in trigonal crystal system. The SEM micrograph of gold-coated pellet sample shows well-defined and homogeneous morphology. Detailed studies of dielectric parameters (εr and tan δ of the compound as a function of temperature and frequency reveal their independence over a wide range of temperature and frequency. The nature of Polarization versus electric field (P–E hysteresis loop of Ba3V2O8 at room temperature suggests its ferroelectric nature. The temperature dependence of pyroelectric coefficient and figure of merits of the sample support its dielectric response. The nature of variation of dc conductivity with temperature confirms the Arrhenius and negative temperature coefficient of resistance (NTCR behavior of the material.

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

Science.gov (United States)

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

2018-04-01

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

Enhancing local absorption within a gold nano-sphere on a dielectric surface under an AFM probe

International Nuclear Information System (INIS)

Talebi Moghaddam, Sina; Ertürk, Hakan; Mengüç, M. Pınar

2016-01-01

This study considers enhancing localized absorption by a gold nanoparticle (NP) placed over a substrate where an atomic force microscope (AFM) tip is in close proximity of the particle. The gold NP and AFM tip are interacting with a surface evanescent wave, resulting a near-field coupling between the tip and NP and consequently enhances the absorption. This concept can be used for selective heating of NPs placed over a surface that enables precise manufacturing at nanometer scales. Different tip positions are considered to identify the optimal tip location and the corresponding enhancement limits. The effects of these interactions on the absorption profiles of dielectric core/gold shell NPs are also studied. It is observed that using core–shell nanoparticles with a dielectric core leads to further enhancement of the absorption efficiency and a more uniform distribution of absorption over the shell. Discrete dipole approximation coupled with surface interactions (DDA-SI) is employed throughout the study, and it is vectorized to improve its computational efficiency. - Highlights: • Plasmonic coupling between solid or core-shell nanoparticles, dielectric surface and Si AFM tip is investigated for achieving localized heating for nano-manufacturing. • Absorption efficiency enhancement limits for core-shell and solid nanoparticles are identified using an AFM tip for surface evanescent wave heating. • The effect of tip location, relative to surface wave direction is outlined, identifying optimal locations, and heat absorption distribution over core-shell and solid nanoparticles. • While using a Si AFM tip enhances absorption, using a dielectric core result in further enhancement in absorption with a more uniform distribution. • DDA-SI-v developed by vectorizing the formulations of DDA-SI for improved computational efficiency.

Directional Emission from Dielectric Leaky-Wave Nanoantennas

Science.gov (United States)

Peter, Manuel; Hildebrandt, Andre; Schlickriede, Christian; Gharib, Kimia; Zentgraf, Thomas; Förstner, Jens; Linden, Stefan

2017-07-01

An important source of innovation in nanophotonics is the idea to scale down known radio wave technologies to the optical regime. One thoroughly investigated example of this approach are metallic nanoantennas which employ plasmonic resonances to couple localized emitters to selected far-field modes. While metals can be treated as perfect conductors in the microwave regime, their response becomes Drude-like at optical frequencies. Thus, plasmonic nanoantennas are inherently lossy. Moreover, their resonant nature requires precise control of the antenna geometry. A promising way to circumvent these problems is the use of broadband nanoantennas made from low-loss dielectric materials. Here, we report on highly directional emission from active dielectric leaky-wave nanoantennas made of Hafnium dioxide. Colloidal semiconductor quantum dots deposited in the nanoantenna feed gap serve as a local light source. The emission patterns of active nanoantennas with different sizes are measured by Fourier imaging. We find for all antenna sizes a highly directional emission, underlining the broadband operation of our design.

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

Directory of Open Access Journals (Sweden)

M. Z. H. Makmud

2018-02-01

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

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

Science.gov (United States)

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

2018-06-01

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

Theoretical Study of Local Surface Plasmon Resonances on a Dielectric-Ag Core-Shell Nanosphere Using the Discrete-Dipole Approximation Method

International Nuclear Information System (INIS)

Ma Ye-Wan; Wu Zhao-Wang; Zhang Li-Hua; Liu Wan-Fang; Zhang Jie

2015-01-01

The local surface plasmon resonances (LSPRs) of dielectric-Ag core-shell nanospheres are studied by the discretedipole approximation method. The result shows that LSPRs are sensitive to the surrounding medium refractive index, which shows a clear red-shift with the increasing surrounding medium refractive index. A dielectric-Ag core-shell nanosphere exhibits a strong coupling between the core and shell plasmon resonance modes. LSPRs depend on the shell thickness and the composition of dielectric-core and metal-shell. LSPRs can be tuned over a longer wavelength range by changing the ratio of core to shell value. The lower energy mode ω_− shows a red-shift with the increasing dielectric-core value and the inner core radius, while blue-shifted with the increasing outer shell thickness. The underlying mechanisms are analyzed with the plasmon hybridization theory and the phase retardation effect. (paper)

Identification of structural relaxation in the dielectric response of water

DEFF Research Database (Denmark)

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

2016-01-01

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

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

DEFF Research Database (Denmark)

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

2012-01-01

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

Dielectric Characteristics of Microstructural Changes and Property Evolution in Engineered Materials

Science.gov (United States)

Clifford, Jallisa Janet

quantitatively using BbDS. These materials are typically used in solid oxide fuel cells (SOFC). Results show significant effect of microstructural design on material properties at multiple temperatures (up to 800 °C). In the later part of the thesis, we will focus on microstructural changes of fiber reinforced composite materials due to impact and static loading. The changes in dielectric response can then be linked to the bulk mechanical properties of the material and various damage modes. Observing trends in dielectric response enables us to further determine local mechanisms and distribution of properties throughout the damaged specimens. A 3D X-ray microscope and a digital microscope have been used to visualize these changes in material microstructure and validate experimental observations. The increase in damage observed in the material microstructure can then also be linked to the changes in dielectric response. Results show that BbDS is an extremely useful tool for identifying microstructural changes within a heterogeneous material and particularly useful in relating remaining properties. Dielectric material variables can be used directly in property degradation laws and help develop a framework for future predictive modeling methodologies.

Local Electronic And Dielectric Properties at Nanosized Interfaces

Energy Technology Data Exchange (ETDEWEB)

Bonnell, Dawn A. [Univ. of Pennsylvania, Philadelphia, PA (United States)

2015-02-23

Final Report to the Department of Energy for period 6/1/2000 to 11/30/2014 for Grant # DE-FG02-00ER45813-A000 to the University of Pennsylvania Local Electronic And Dielectric Properties at Nanosized Interfaces PI: Dawn Bonnell The behavior of grain boundaries and interfaces has been a focus of fundamental research for decades because variations of structure and composition at interfaces dictate mechanical, electrical, optical and dielectric properties in solids. Similarly, the consequence of atomic and electronic structures of surfaces to chemical and physical interactions are critical due to their implications to catalysis and device fabrication. Increasing fundamental understanding of surfaces and interfaces has materially advanced technologies that directly bear on energy considerations. Currently, exciting developments in materials processing are enabling creative new electrical, optical and chemical device configurations. Controlled synthesis of nanoparticles, semiconducting nanowires and nanorods, optical quantum dots, etc. along with a range of strategies for assembling and patterning nanostructures portend the viability of new devices that have the potential to significantly impact the energy landscape. As devices become smaller the impact of interfaces and surfaces grows geometrically. As with other nanoscale phenomena, small interfaces do not exhibit the same properties as do large interfaces. The size dependence of interface properties had not been explored and understanding at the most fundamental level is necessary to the advancement of nanostructured devices. An equally important factor in the behavior of interfaces in devices is the ability to examine the interfaces under realistic conditions. For example, interfaces and boundaries dictate the behavior of oxide fuel cells which operate at extremely high temperatures in dynamic high pressure chemical environments. These conditions preclude the characterization of local properties during fuel cell

Characterization of dielectric materials

Energy Technology Data Exchange (ETDEWEB)

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

2017-06-27

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

Dielectric dispersion in pure and doped lithium rubidium sulphate

Science.gov (United States)

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

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

Surface Plasmon-Mediated Nanoscale Localization of Laser-Driven sub-Terahertz Spin Dynamics in Magnetic Dielectrics

Science.gov (United States)

Chekhov, Alexander L.; Stognij, Alexander I.; Satoh, Takuya; Murzina, Tatiana V.; Razdolski, Ilya; Stupakiewicz, Andrzej

2018-05-01

Ultrafast all-optical control of spins with femtosecond laser pulses is one of the hot topics at the crossroads of photonics and magnetism with a direct impact on future magnetic recording. Unveiling light-assisted recording mechanisms for an increase of the bit density beyond the diffraction limit without excessive heating of the recording medium is an open challenge. Here we show that surface plasmon-polaritons in hybrid metal-dielectric structures can provide spatial confinement of the inverse Faraday effect, mediating the excitation of localized coherent spin precession with 0.41 THz frequency. We demonstrate a two orders of magnitude enhancement of the excitation efficiency at the surface plasmon resonance within the 100 nm layer in dielectric garnet. Our findings broaden the horizons of ultrafast spin-plasmonics and open pathways towards non-thermal opto-magnetic recording at the nano-scale.

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

Directory of Open Access Journals (Sweden)

B. Zazoum

2013-01-01

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

Dielectric platforms for surface-enhanced spectroscopies (Conference Presentation)

Science.gov (United States)

Maier, Stefan A.

2016-03-01

Plasmonic nanostructures serve as the main backbone of surface enhanced sensing methodologies, yet the associated optical losses lead to localized heating as well as quenching of molecules, complicating their use for enhancement of fluorescent emission. Additionally, conventional plasmonic materials are limited to operation in the visible part of the spectrum. We will elucidate how nanostructures consisting of conventional and polar dielectrics can be employed as a highly promising alternative platform. Dielectric nanostructures can sustain scattering resonances due to both electric and magnetic Mie modes. We have recently predicted high enhanced local electromagnetic field hot spots in dielectric nanoantenna dimers, with the hallmark of spot sizes comparable to those achievable with plasmonic antennas, but with lower optical losses. Here, we will present first experimental evidence for both fluorescence and Raman enhancement in dielectric nanoantennas, including a direct determination of localized heating, and compare to conventional Au dimer antennas. The second part of the talk will focus on the mid-infrared regime of the electromagnetic spectrum, outlining possibilities for surface enhanced infrared absorption spectroscopy based on polar and hyperbolic dielectrics.

Frequency and temperature dependent dielectric properties of TiO2-V2O5 nanocomposites

Science.gov (United States)

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

2018-03-01

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

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

International Nuclear Information System (INIS)

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

1988-10-01

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

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

International Nuclear Information System (INIS)

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

2015-01-01

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

Dielectric function of two-phase colloid-polymer nanocomposite.

Science.gov (United States)

Mitzscherling, S; Cui, Q; Koopman, W; Bargheer, M

2015-11-28

The plasmon resonance of metal nanoparticles determines their optical response in the visible spectral range. Many details such as the electronic properties of gold near the particle surface and the local environment of the particles influence the spectra. We show how the cheap but highly precise fabrication of composite nanolayers by spin-assisted layer-by-layer deposition of polyelectrolytes can be used to investigate the spectral response of gold nanospheres (GNS) and gold nanorods (GNR) in a self-consistent way, using the established Maxwell-Garnett effective medium (MGEM) theory beyond the limit of homogeneous media. We show that the dielectric function of gold nanoparticles differs from the bulk value and experimentally characterize the shape and the surrounding of the particles thoroughly by SEM, AFM and ellipsometry. Averaging the dielectric functions of the layered surrounding by an appropriate weighting with the electric field intensity yields excellent agreement for the spectra of several nanoparticles and nanorods with various cover-layer thicknesses.

Tuning the dielectric properties of polystyrene/poly(vinylidene fluoride) blends by selectively localizing carbon black nanoparticles.

Science.gov (United States)

Zhao, Xiaodong; Zhao, Jun; Cao, Jian-Ping; Wang, Xiaoyan; Chen, Min; Dang, Zhi-Min

2013-02-28

In this work, the dielectric properties of immiscible polystyrene (PS)/poly(vinylidene fluoride) (PVDF) blends are tuned by selectively localizing carbon black (CB) nanoparticles in different phases. The PS/PVDF blends have a wide window of cocontinuity (ca. 30-80 vol % in terms of the volume fraction of PS component (v(PS))). The selective localization of CB nanoparticles is achieved by using the masterbatch process during melt mixing. For the volume ratio PS/PVDF 1/1 and the volume fraction of CB nanoparticles (v(CB)) below but close to the percolation threshold (v(c)(CB)), the selective localization of CB nanoparticles in PVDF phase produces higher dielectric constant (ε) than that in PS phase, whereas the ε of the ternary mixtures without selective localization of fillers is in the middle. For the volume ratios PS/PVDF 1/2 and 2/1, the selective location of CB nanoparticles in different phases can be used to easily tune the system from conductive to insulating or inverse, which might have potential applications in industry. The fillers are found to be "fixed" in the masterbatch of PS or PVDF component and there is no migration of the fillers to another phase occurring during the further mixing process for the mixing time up to 30 min. Furthermore, the addition of CB nanoparticles to the polymer matrix is found to induce the brittle-ductile transition in the system and increase the compatibility between the immiscible PS and PVDF components, which should benefit the mechanical properties.

Microscopic theoretical study of frequency dependent dielectric constant of heavy fermion systems

Science.gov (United States)

Shadangi, Keshab Chandra; Rout, G. C.

2017-05-01

The dielectric polarization and the dielectric constant plays a vital role in the deciding the properties of the Heavy Fermion Systems. In the present communication we consider the periodic Anderson's Model which consists of conduction electron kinetic energy, localized f-electron kinetic energy and the hybridization between the conduction and localized electrons, besides the Coulomb correlation energy. We calculate dielectric polarization which involves two particle Green's functions which are calculated by using Zubarev's Green's function technique. Using the equations of motion of the fermion electron operators. Finally, the temperature and frequency dependent dielectric constant is calculated from the dielectric polarization function. The charge susceptibility and dielectric constant are computed numerically for different physical parameters like the position (Ef) of the f-electron level with respect to fermi level, the strength of the hybridization (V) between the conduction and localized f-electrons, Coulomb correlation potential temperature and optical phonon wave vector (q). The results will be discussed in a reference to the experimental observations of the dielectric constants.

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Local-Field Distribution of Two Dielectric Inclusions at Small Separation

Science.gov (United States)

Siu, Yuet-Lun; Yu, Kin-Wah

2001-03-01

When two dielectric inclusions approach to each other in a composite medium, significant mutual polarization effects must occur. These effects are multipolar in nature and are difficult to treat from first principles(J. D. Jackson, Classical Electrodynamics), 2nd edition, (Wiley, New York, 1975).. In this work, we employ the discrete-dipole theory(B. T. Draine and P. J. Flatau, J. Opt. Soc. Am. A 11) 1491 (1994). to account for the mutual polarization effects by dividing the inclusions into many small subparts. We begin the calculation at small inclusion sizes and large separation, where the point-dipole limit being valid, and proceed to larger inclusion sizes and small separation, for which the mutual polarization effect becomes important. Then, we apply the theory to determine the dipole moment of each subpart self-consistently. In this way, each dipole moment yields the local electric field, which in turn polarizes the neighboring dipoles. We also begin the calculation at small inclusion sizes and large separation, where the point-dipole limit being valid, and proceed to larger inclusion sizes and small separation. Our resluts indicate that convergence is achieved with moderate computational effects. The results produce valuable information about the local electric field distribution, which is relevant to optical absorption due to surface phonon-polaritons of ionic microcrystals.

Dielectric nanoresonators for light manipulation

Science.gov (United States)

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

2017-07-01

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

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

International Nuclear Information System (INIS)

Ngai, K. L.

2015-01-01

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

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

Science.gov (United States)

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

2018-04-01

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

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

International Nuclear Information System (INIS)

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

1994-01-01

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

Hydrostatic pressure effects on the dielectric response of potassium cyanide

International Nuclear Information System (INIS)

Ortiz Lopez, J.

1992-01-01

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

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

Science.gov (United States)

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

2014-07-08

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

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

Science.gov (United States)

Umari, Paolo

2006-03-01

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

Thickness-Dependent Dielectric Constant of Few-Layer In 2 Se 3 Nanoflakes

KAUST Repository

Wu, Di

2015-11-17

© 2015 American Chemical Society. The dielectric constant or relative permittivity (εr) of a dielectric material, which describes how the net electric field in the medium is reduced with respect to the external field, is a parameter of critical importance for charging and screening in electronic devices. Such a fundamental material property is intimately related to not only the polarizability of individual atoms but also the specific atomic arrangement in the crystal lattice. In this Letter, we present both experimental and theoretical investigations on the dielectric constant of few-layer In2Se3 nanoflakes grown on mica substrates by van der Waals epitaxy. A nondestructive microwave impedance microscope is employed to simultaneously quantify the number of layers and local electrical properties. The measured εr increases monotonically as a function of the thickness and saturates to the bulk value at around 6-8 quintuple layers. The same trend of layer-dependent dielectric constant is also revealed by first-principles calculations. Our results of the dielectric response, being ubiquitously applicable to layered 2D semiconductors, are expected to be significant for this vibrant research field.

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-05-15

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

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

Science.gov (United States)

Van Eester, Dirk

2005-03-01

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

Stretched exponential relaxation and ac universality in disordered dielectrics

DEFF Research Database (Denmark)

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

2007-01-01

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

Surface structures and dielectric response of ultrafine BaTiO3 particles

International Nuclear Information System (INIS)

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

1998-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-03-21

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-07-11

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

UV response on dielectric properties of nano nematic liquid crystal

Directory of Open Access Journals (Sweden)

Kamal Kumar Pandey

2018-03-01

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

Dielectric polarization in random media

International Nuclear Information System (INIS)

Ramshaw, J.D.

1984-01-01

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

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

Directory of Open Access Journals (Sweden)

Tianhuan Luo

2015-01-01

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

Oblique surface waves at an interface between a metal-dielectric superlattice and an isotropic dielectric

International Nuclear Information System (INIS)

Vuković, Slobodan M; Miret, Juan J; Zapata-Rodriguez, Carlos J; Jakšić, Zoran

2012-01-01

We investigate the existence and dispersion characteristics of surface waves that propagate at an interface between a metal-dielectric superlattice and an isotropic dielectric. Within the long-wavelength limit, when the effective-medium (EM) approximation is valid, the superlattice behaves like a uniaxial plasmonic crystal with the main optical axes perpendicular to the metal-dielectric interfaces. We demonstrate that if such a semi-infinite plasmonic crystal is cut normally to the layer interfaces and brought into contact with a semi-infinite dielectric, a new type of surface mode can appear. Such modes can propagate obliquely to the optical axes if favorable conditions regarding the thickness of the layers and the dielectric permittivities of the constituent materials are met. We show that losses within the metallic layers can be substantially reduced by making the layers sufficiently thin. At the same time, a dramatic enlargement of the range of angles for oblique propagation of the new surface modes is observed. This can lead, however, to field non-locality and consequently to failure of the EM approximation.

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

International Nuclear Information System (INIS)

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

1979-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-07-01

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

Local field in finite-size metamaterials

DEFF Research Database (Denmark)

Bordo, Vladimir

2018-01-01

The theory of the optical response of a metamaterial slab which is represented by metal nanoparticles embedded in a dielectric matrix is developed. It is demonstrated that the account of the reflections from the slab boundaries essentially modifies the local field in the slab and leads...

Ionic Structure at Dielectric Interfaces

Science.gov (United States)

Jing, Yufei

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

Nanostructure multilayer dielectric materials for capacitors and insulators

Science.gov (United States)

Barbee, Jr., Troy W.; Johnson, Gary W.

1998-04-21

A capacitor is formed of at least two metal conductors having a multilayer dielectric and opposite dielectric-conductor interface layers in between. The multilayer dielectric includes many alternating layers of amorphous zirconium oxide (ZrO.sub.2) and alumina (Al.sub.2 O.sub.3). The dielectric-conductor interface layers are engineered for increased voltage breakdown and extended service life. The local interfacial work function is increased to reduce charge injection and thus increase breakdown voltage. Proper material choices can prevent electrochemical reactions and diffusion between the conductor and dielectric. Physical vapor deposition is used to deposit the zirconium oxide (ZrO.sub.2) and alumina (Al.sub.2 O.sub.3) in alternating layers to form a nano-laminate.

Electromechanical response of silicone dielectric elastomers

Science.gov (United States)

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

2016-08-01

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

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

DEFF Research Database (Denmark)

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

2004-01-01

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

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

DEFF Research Database (Denmark)

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

2005-01-01

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

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

International Nuclear Information System (INIS)

Hao Jian; Liao Ruijin; Chen, George

2011-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2011-08-12

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

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

International Nuclear Information System (INIS)

Do-Amaral-De-Andrade-Sophia, Gustavo

2014-01-01

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

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

Science.gov (United States)

Lefèvre, Victor; Lopez-Pamies, Oscar

2017-02-01

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

Nonlinear dielectric response in ferroelectric thin films

Directory of Open Access Journals (Sweden)

Lente, M. H.

2004-08-01

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

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

Mixed-space formalism for the dielectric response in periodic systems

International Nuclear Information System (INIS)

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

1995-01-01

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

Dielectric spectroscopy of Ag-starch nanocomposite films

Science.gov (United States)

Meena; Sharma, Annu

2018-04-01

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

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

International Nuclear Information System (INIS)

Liang, Pengfei; Yang, Zupei; Chao, Xiaolian

2016-01-01

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

Electromagnetic properties of metal-dielectric media and their applications

Science.gov (United States)

Animilli, Shravan Rakesh

The main objective of this dissertation is to investigate nano-structured random composite materials, which exhibit anomalous phenomena, such as the extraordinary enhancements of linear and non-linear optical processes due to excitation of collective electronic states, surface plasmons (SP). The main goal is to develop a time and memory efficient novel numerical method to study the properties of these random media in three dimensions (3D) by utilization of multi core processing and packages such as MPI for parallel execution. The developed numerical studies are then utilized to provide a comprehensive characterization and optimization of a surface plasmon enhanced solar cell (SPESC) and to serve as a test bed for enhanced bio and chemical sensing. In this context, this thesis work develops an efficient and exact numerical algorithm here referred to as Block Elimination Method (BE) which provides the unique capability of modeling extremely large scale composite materials (with up to 1 million strongly interacting metal or dielectric particles). This capability is crucial in order to study the electromagnetic response of large scale inhomogeneous (fractal) films and bulk composites at critical concentrations (percolation). The developed numerical method is used to accurately estimate parameters that describe the composite materials, including the effective conductivity and correlation length scaling exponents, as well as density of states and localization length exponents at the band center. This works reveals, for a first time, a unique de-localization mechanism that plays an important role in the excitation of charge-density waves, i.e. surface plasmons (SP), in metal-dielectric composites. It also shows that in 3D metal-dielectric percolation systems the local fields distribution function for frequencies close to the single particle plasmon resonance is log-normal which is a signature of a metal-dielectric phase transition manifested in the optical response of the

Laser amplification in excited dielectrics

Science.gov (United States)

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

2018-01-01

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

Nanocomposite dielectrics-properties and implications

Energy Technology Data Exchange (ETDEWEB)

Nelson, J K; Hu, Y [Department of Electrical, Computer and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States)

2005-01-21

The incorporation of nanoparticles into thermosetting resins is seen to impart desirable dielectric properties when compared with conventional (micron-sized particulates) composites. Although the improvements are accompanied by the mitigation of internal charge in the materials, the nature of the interfacial region is shown to be pivotal in determining the dielectric behaviour. In particular, it is shown that the conditions and enhanced area of the interface changes the bonding that may give rise to an interaction zone, which affects the interfacial polarization through the formation of local conductivity.

Temperature Effects of Dielectric Properties of ER Fluids

Science.gov (United States)

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

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

Investigation of steel to dielectric transition using microminiature eddy-current converter

Directory of Open Access Journals (Sweden)

Malikov Vladimir

2018-01-01

Full Text Available The research aims to develop a microminiature converter for electrical steel investigation. The research topic is considered relevant due to the need for evaluation and forecasting of safe operating life of electric steel products. The authors determined the capability to study steel characteristics at different depths based on variations of eddy-current converter amplitude at the steel-dielectric boundary. A microminiature transformer-type converter was designed, which enables to perform local investigations of ferromagnetic materials using eddy-current method based on local studies of the steel electrical conductivity. Having the designed converter as a basis, a hardware-software complex was built to perform experimental studies of steel at the interface boundary. A system was developed for automated converter relocation above the studied object at a specified velocity. Test results are reported for a specimen with continuous and discrete measurements taken at different frequencies. Response dependence of eddy-current converter was found to demonstrate non-linear behavior at steel to dielectric transition. The effect of gap between the eddy-current converter and the test object is investigated.

Experimental Characterization of Dielectric Properties in Fluid Saturated Artificial Shales

Directory of Open Access Journals (Sweden)

Roman Beloborodov

2017-01-01

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

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

NARCIS (Netherlands)

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

2009-01-01

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

Muscle-like high-stress dielectric elastomer actuators with oil capsules

International Nuclear Information System (INIS)

La, Thanh-Giang; Lau, Gih-Keong; Shiau, Li-Lynn; Wei-Yee Tan, Adrian

2014-01-01

Despite being capable of generating large strains, dielectric elastomer actuators (DEAs) are short of strength. Often, they cannot produce enough stress or as much work as that achievable by human elbow muscles. Their maximum actuation capacity is limited by the electrical breakdown of dielectric elastomers. Often, failures of these soft actuators are pre-mature and localized at the weakest spot under high field and high stress. Localized breakdowns, such as electrical arcing, thermal runaway and punctures, could spread to ultimately cause rupture if they were not stopped. This work shows that dielectric oil immersion and self-clearable electrodes nibbed the buds of localized breakdowns from DEAs. Dielectric oil encapsulation in soft-membrane capsules was found to help the DEA sustain an ultra-high electrical breakdown field of 835 MVm −1 , which is 46% higher than the electrical breakdown strength of the dry DEA in air at 570 MV m −1 . Because of the increased apparent dielectric strength, this oil-capsuled DEA realizes a higher maximum isotonic work density of up to 31.51Jkg −1 , which is 43.8% higher than that realized by the DEA in air. Meanwhile, it produces higher maximum isometric stress of up to 1.05 MPa, which is 75% higher than that produced by the DEA in air. Such improved actuator performances are comparable to those achieved by human flexor muscles, which can exert up to 1.2 MPa during elbow flexion. This muscle-like, high-stress dielectric elastomeric actuation is very promising to drive future human-like robots. (paper)

Dielectric response of particle-antiparticle plasmas in a magnetic field

International Nuclear Information System (INIS)

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

1982-01-01

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

DIELECTRIC WAKE FIELD RESONATOR ACCELERATOR MODULE

Energy Technology Data Exchange (ETDEWEB)

Hirshfield, Jay L.

2013-11-06

Results are presented from experiments, and numerical analysis of wake fields set up by electron bunches passing through a cylindrical or rectangular dielectric-lined structure. These bunches excite many TM-modes, with Ez components of the wake fields sharply localized on the axis of the structure periodically behind the bunches. The experiment with the cylindrical structure, carried out at ATF Brookhaven National Laboratory, used up to three 50 MeV bunches spaced by one wake field period (21 cm) to study the superposition of wake fields by measuring the energy loss of each bunch after it passed through the 53-cm long dielectric element. The millimeter-wave spectrum of radiation excited by the passage of bunches is also studied. Numerical analysis was aimed not only to simulate the behavior of our device, but in general to predict dielectric wake field accelerator performance. It is shown that one needs to match the radius of the cylindrical dielectric channel with the bunch longitudinal rms-length to achieve optimal performance.

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

International Nuclear Information System (INIS)

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

2012-01-01

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

Influence of the local structure in phase-change materials on their dielectric permittivity.

Science.gov (United States)

Shportko, Kostiantyn V; Venger, Eugen F

2015-01-01

Ge-Sb-Te alloys, which belong to the phase-change materials, are promising materials for data storage and display and data visualization applications due to their unique properties. This includes a remarkable difference of their electrical and optical properties in the amorphous and crystalline state. Pronounced change of optical properties for Ge-Sb-Te alloys is linked to the different bonding types and different atomic arrangements in amorphous and crystalline states. The dielectric function of phase-change materials has been investigated in the far infrared (FIR) range. Phonons have been detected by FTIR spectroscopy. Difference of the dispersion of the dielectric permittivity of amorphous and crystalline samples is caused by different structures in different states which contribute to the dielectric permittivity.

Photoinduced Giant Dielectric Constant in Lead Halide Perovskite Solar Cells.

Science.gov (United States)

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

2014-07-03

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

Hydrodynamical flows in dielectric liquid in strong inhomogeneous pulsed electric field

International Nuclear Information System (INIS)

Tereshonok, Dmitry V; Babaeva, Natalia Yu; Naidis, George V; Smirnov, Boris M

2016-01-01

We consider a hydrodynamical flow of dielectric liquid near a high voltage needle-shaped electrode in a strong inhomogeneous pulsed electric field. It was shown that under a small rise time, a negative pressure area (pressure is less than critical pressure) appears near the electrode leading to the formation of a cavity in which electric breakdown can develop. A comparison of the dependence of the velocity of fluid near an electrode for two cases (taking into account the dependence of dielectric permeability of the liquid on the electric field and without taking it into account) was made. A field-dependent dielectric coefficient leads to the appearance of two local maximums of the velocities and increases the minimum pressure, thus lowering the possibility of cavitation. While under the constant value of dielectric permeability only one local maximum appears. (paper)

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

International Nuclear Information System (INIS)

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

2014-01-01

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

Tribo-electric charging of dielectric solids of identical composition

Science.gov (United States)

Angus, John C.; Greber, Isaac

2018-05-01

Despite its long history and importance in many areas of science and technology, there is no agreement on the mechanisms responsible for tribo-electric charging, including especially the tribo-charging of chemically identical dielectric solids. Modeling of the excitation, diffusional transport, and de-excitation of electrons from hot spots shows that a difference in local surface roughness of otherwise identical solid dielectric objects leads to different transient excited electron concentrations during tribo-processes. The model predicts that excited electron concentrations are lower and concentration gradients higher in solids with rougher rather than smoother surfaces. Consequently, during contact, the flux of charge carriers (electrons or holes) from hot spots will be greater into the rougher solid than into the smoother solid. These predictions are in agreement with current and historical observations of tribo-electric charge transfer between solids of the same composition. This effect can take place in parallel with other processes and may also play a role in the charging of solids of different composition.

Correlation of Bulk Dielectric and Piezoelectric Properties to the Local Scale Phase Transformations, Domain Morphology, and Crystal Structure Modified

Energy Technology Data Exchange (ETDEWEB)

Priya, Shashank [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Viehland, Dwight [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)

2014-12-14

Three year program entitled “Correlation of bulk dielectric and piezoelectric properties to the local scale phase transformations, domain morphology, and crystal structure in modified lead-free grain-textured ceramics and single crystals” was supported by the Department of Energy. This was a joint research program between D. Viehland and S. Priya at Virginia Tech. Single crystal and textured ceramics have been synthesized and characterized. Our goals have been (i) to conduct investigations of lead-free piezoelectric systems to establish the local structural and domain morphologies that result in enhanced properties, and (ii) to synthesize polycrystalline and grain oriented ceramics for understanding the role of composition, microstructure, and anisotropy

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-04-05

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

First-principles study of dielectric properties of cerium oxide

International Nuclear Information System (INIS)

Yamamoto, Takenori; Momida, Hiroyoshi; Hamada, Tomoyuki; Uda, Tsuyoshi; Ohno, Takahisa

2005-01-01

We have theoretically investigated the dielectric properties of fluorite CeO 2 as well as hexagonal and cubic Ce 2 O 3 by using first-principles pseudopotentials techniques within the local density approximation. Calculated electronic and lattice dielectric constants of CeO 2 are in good agreement with previous theoretical and experimental results. For Ce 2 O 3 , the hexagonal phase has a lattice dielectric constant comparable to that of CeO 2 , whereas the cubic phase has a much smaller one. We have concluded that the enhancement of the dielectric constant in CeO 2 epitaxially grown on Si is not due to its lattice expansion experimentally observed nor regular formation of oxygen vacancies in CeO 2

Plasmonic versus dielectric enhancement in thin-film solar cells

DEFF Research Database (Denmark)

Dühring, Maria Bayard; Mortensen, N. Asger; Sigmund, Ole

2012-01-01

to its metallic counterpart. We show that the enhanced normalized short-circuit current for a cell with silicon strips can be increased 4 times compared to the best performance for strips of silver, gold, or aluminium. For this particular case, the simple dielectric grating may outperform its plasmonic......Several studies have indicated that broadband absorption of thin-film solar cells can be enhanced by use of surface-plasmon induced resonances of metallic parts like strips or particles. The metallic parts may create localized modes or scatter incoming light to increase absorption in thin......-film semiconducting material. For a particular case, we show that coupling to the same type of localized slab-waveguide modes can be obtained by a surface modulation consisting of purely dielectric strips. The purely dielectric device turns out to have a significantly higher broadband enhancement factor compared...

A dielectric approach to high temperature superconductivity

International Nuclear Information System (INIS)

Mahanty, J.; Das, M.P.

1989-01-01

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

Experimental Characterization of Dielectric Properties in Fluid Saturated Artificial Shales

OpenAIRE

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

2017-01-01

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

Infrared and THz spectroscopy of nanostructured dielectrics

Directory of Open Access Journals (Sweden)

Jan Petzelt

2009-09-01

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

Plasmonic and Dielectric Metasurfaces: Design, Fabrication and Applications

Directory of Open Access Journals (Sweden)

Jian Wang

2016-09-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-06-25

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

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

International Nuclear Information System (INIS)

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

2013-01-01

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

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

Directory of Open Access Journals (Sweden)

O. Zhuromskyy

2011-09-01

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

The polarization response function and the dielectric permittivity of a plasma

International Nuclear Information System (INIS)

Gnavi, G.; Gratton, F.

1984-01-01

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

Gold nanoparticles extraction from dielectric scattering background

Science.gov (United States)

Hong, Xin; Wang, Jingxin

2014-11-01

The unique advantages such as brightness, non-photobleaching, good bio-compatibility make gold nanoparticles desirable labels and play important roles in biotech and related research and applications. Distinguishing gold nanoparticles from other dielectric scattering particles is of more importance, especially in bio-tracing and imaging. The enhancement image results from the localized surface plasmon resonance associated with gold nanopartilces makes themselves distinguishable from other dielectric particles, based on which, we propose a dual-wavelength detection method by employing a high sensitive cross-polarization microscopy.

Super dielectric capacitor using scaffold dielectric

OpenAIRE

Phillips, Jonathan

2018-01-01

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

Method of making dielectric capacitors with increased dielectric breakdown strength

Science.gov (United States)

Ma, Beihai; Balachandran, Uthamalingam; Liu, Shanshan

2017-05-09

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

Toward superlensing with metal-dielectric composites and multilayers

DEFF Research Database (Denmark)

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

2010-01-01

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

Macroscopic optical response and photonic bands

International Nuclear Information System (INIS)

Pérez-Huerta, J S; Luis Mochán, W; Ortiz, Guillermo P; Mendoza, Bernardo S

2013-01-01

We develop a formalism for the calculation of the macroscopic dielectric response of composite systems made of particles of one material embedded periodically within a matrix of another material, each of which is characterized by a well-defined dielectric function. The nature of these dielectric functions is arbitrary, and could correspond to dielectric or conducting, transparent or opaque, absorptive and dispersive materials. The geometry of the particles and the Bravais lattice of the composite are also arbitrary. Our formalism goes beyond the long-wavelength approximation as it fully incorporates retardation effects. We test our formalism through the study of the propagation of electromagnetic waves in two-dimensional photonic crystals made of periodic arrays of cylindrical holes in a dispersionless dielectric host. Our macroscopic theory yields a spatially dispersive macroscopic response which allows the calculation of the full photonic band structure of the system, as well as the characterization of its normal modes, upon substitution into the macroscopic field equations. We can also account approximately for the spatial dispersion through a local magnetic permeability and analyze the resulting dispersion relation, obtaining a region of left handedness. (paper)

Dielectric Response of Corn Leaves to Water Stress

NARCIS (Netherlands)

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

2016-01-01

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

High resolution imaging of dielectric surfaces with an evanescent field optical microscope

NARCIS (Netherlands)

van Hulst, N.F.; Segerink, Franciscus B.; Bölger, B.

1992-01-01

An evanescent field optical microscope (EFOM) is presented which employs frustrated total internal reflection o­n a localized scale by scanning a dielectric tip in close proximity to a sample surface. High resolution images of dielectric gratings and spheres containing both topographic and

Spontaneous emission from active dielectric microstructures

DEFF Research Database (Denmark)

Søndergaard, Thomas; Tromborg, Bjarne

2001-01-01

and engineered due to the dependence of the emission rate on the location and polarisation of the emitters in the structure. This paper addresses the methods of quantum electrodynamics of dielectric media which enable calculation of the local rate of spontaneous emission in active microstructures....

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

Directory of Open Access Journals (Sweden)

Chian Heng Lee

2014-10-01

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

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

Directory of Open Access Journals (Sweden)

Lin Zhang

2017-06-01

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

Exciton center-of-mass localization and dielectric environment effect in monolayer WS2

Science.gov (United States)

Hichri, Aïda; Ben Amara, Imen; Ayari, Sabrine; Jaziri, Sihem

2017-06-01

The ultrathin transition metal dichalcogenides (TMDs) have emerged as promising materials for various applications using two dimensional semiconductors. They have attracted increasing attention due to their unique optical properties originate from neutral and charged excitons. In this paper, we study the strong localization of exciton center-of-mass motion within random potential fluctuations caused by the monolayer defects. Here, we report negatively charged exciton formation in monolayer TMDs, notably tungsten disulfide WS2. Our theory is based on an effective mass model of neutral and charged excitons, parameterized by ab-initio calculations. Taking into the account the strong correlation between the monolayer WS2 and the surrounding dielectric environment, our theoretical results are in good agreement with one-photon photoluminescence (PL) and reflectivity measurements. We also show that the exciton state with p-symmetry, experimentally observed by two-photon PL emission, is energetically below the 2s-state. We use the equilibrium mass action law, to quantify the relative weight of exciton and trion PL. We show that exciton and trion emission can be tuned and controlled by external parameters like temperature, pumping, and injection electrons. Finally, in comparison with experimental measurements, we show that exciton emission in monolayer tungsten dichalcogenides is substantially reduced. This feature suggests that free exciton can be trapped in disordered potential wells to form a localized exciton and therefore offers a route toward novel optical properties.

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

Science.gov (United States)

Levy, Amir; Andelman, David; Orland, Henri

2012-06-01

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

Millimeter wave and terahertz dielectric properties of biological materials

Science.gov (United States)

Khan, Usman Ansar

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

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

International Nuclear Information System (INIS)

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

2012-01-01

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

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

CERN Document Server

Bouamrane, R

2003-01-01

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

Localized states in advanced dielectrics from the vantage of spin- and symmetry-polarized tunnelling across MgO.

Science.gov (United States)

Schleicher, F; Halisdemir, U; Lacour, D; Gallart, M; Boukari, S; Schmerber, G; Davesne, V; Panissod, P; Halley, D; Majjad, H; Henry, Y; Leconte, B; Boulard, A; Spor, D; Beyer, N; Kieber, C; Sternitzky, E; Cregut, O; Ziegler, M; Montaigne, F; Beaurepaire, E; Gilliot, P; Hehn, M; Bowen, M

2014-08-04

Research on advanced materials such as multiferroic perovskites underscores promising applications, yet studies on these materials rarely address the impact of defects on the nominally expected materials property. Here, we revisit the comparatively simple oxide MgO as the model material system for spin-polarized solid-state tunnelling studies. We present a defect-mediated tunnelling potential landscape of localized states owing to explicitly identified defect species, against which we examine the bias and temperature dependence of magnetotransport. By mixing symmetry-resolved transport channels, a localized state may alter the effective barrier height for symmetry-resolved charge carriers, such that tunnelling magnetoresistance decreases most with increasing temperature when that state is addressed electrically. Thermal excitation promotes an occupancy switchover from the ground to the excited state of a defect, which impacts these magnetotransport characteristics. We thus resolve contradictions between experiment and theory in this otherwise canonical spintronics system, and propose a new perspective on defects in dielectrics.

Materials Fundamentals of Gate Dielectrics

CERN Document Server

Demkov, Alexander A

2006-01-01

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

Dielectric matrix, dynamical matrix and phonon dispersion in hcp transition metal scandium

International Nuclear Information System (INIS)

Singh, Joginder; Singh, Natthi; Prakash, S.

1976-01-01

Complete dielectric matrix is evaluated for hcp transition metal scandium using the non-interacting s- and d-band model. The local field corrections which are consequence of the non-diagonal part of the dielectric matrix are calculated explicitly. The free electron approximation is used for the s-electrons and the simple tight-binding approximation is used for the d-electrons. The theory developed by Singh and others is used to invert the dielectric matrix and the explicit expressions for the dynamical matrix are obtained. The phonon dispersion relations are investigated by using the renormalized Animalu transition metal model potential (TMMP) for bare ion potential. The contribution due to non-central forces which arise due to local fields is found to be 20%. The results are found in resonably good agreement with the experimental values. (author)

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

DEFF Research Database (Denmark)

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

2016-01-01

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

Color-dielectric model as an explanation of the Nolen-Schiffer anomaly

International Nuclear Information System (INIS)

Williams, A.G.; Thomas, A.W.

1986-01-01

We discuss the quantum chromodynamically motivated color-dielectric model originally proposed by Nielsen and Patkos and show, using some straightforward approximations, that it can lead to charge-symmetry breaking effects in nuclei. We then show, using a local density approximation and standard nuclear structure properties, that for suitable choices of parameters this color-dielectric model can explain the Nolen-Schiffer anomaly

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

International Nuclear Information System (INIS)

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

2016-01-01

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

Quantitative nanometer-scale mapping of dielectric tunability

Energy Technology Data Exchange (ETDEWEB)

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

2015-08-21

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

The Dielectric Behavior of Cyano-Substituted Poly imides

International Nuclear Information System (INIS)

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

2013-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-03-25

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

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

International Nuclear Information System (INIS)

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

2005-01-01

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

Strain tunable ferroelectric and dielectric properties of BaZrO3

International Nuclear Information System (INIS)

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

2014-01-01

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

Optical dielectric function of intrinsic amorphous silicon

International Nuclear Information System (INIS)

Ching, W.Y.; Lin, C.C.

1978-01-01

The imaginary part of the optical dielectric function epsilon 2 (ω) has been calculated using a continuous-random-tetrahedral network as the structural model for the atomic positions. Here the electronic energies and wave functions are determined by first-principles calculations with the method of linear combinations of atomic orbitals (LCAO), and the momentum matrix elements are evaluated directly from the LCAO wave functions. The calculated dielectric function is in good overall agreement with experiment. At energies within 1 eV above the threshold, the epsilon 2 curve shows some structures that are due to interband transitions between the localized states near the band gap

Non-linear dielectric monitoring of biological suspensions

International Nuclear Information System (INIS)

Treo, E F; Felice, C J

2007-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-01-21

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

Local Responsiveness in Distant Markets

DEFF Research Database (Denmark)

Lubinski, Christina

2015-01-01

Multinational corporations face the challenge of balancing global integration and local responsiveness. Localization strategies have been much debated in the literature, and scholars have suggested the 1980s as a watershed moment leading to the development of distinctly transnational companies se......, the political context, and the flow of information between headquarters and subsidiaries showing how and why these companies developed into transnational entities.......Multinational corporations face the challenge of balancing global integration and local responsiveness. Localization strategies have been much debated in the literature, and scholars have suggested the 1980s as a watershed moment leading to the development of distinctly transnational companies...... on the Indian market before WWI, this article traces the competition between different Western gramophone companies and their business strategies for this economically attractive market with institutional voids and rising Indian nationalism. It addresses the specificity of the gramophone and music industry...

Automated general temperature correction method for dielectric soil moisture sensors

Science.gov (United States)

Kapilaratne, R. G. C. Jeewantinie; Lu, Minjiao

2017-08-01

An effective temperature correction method for dielectric sensors is important to ensure the accuracy of soil water content (SWC) measurements of local to regional-scale soil moisture monitoring networks. These networks are extensively using highly temperature sensitive dielectric sensors due to their low cost, ease of use and less power consumption. Yet there is no general temperature correction method for dielectric sensors, instead sensor or site dependent correction algorithms are employed. Such methods become ineffective at soil moisture monitoring networks with different sensor setups and those that cover diverse climatic conditions and soil types. This study attempted to develop a general temperature correction method for dielectric sensors which can be commonly used regardless of the differences in sensor type, climatic conditions and soil type without rainfall data. In this work an automated general temperature correction method was developed by adopting previously developed temperature correction algorithms using time domain reflectometry (TDR) measurements to ThetaProbe ML2X, Stevens Hydra probe II and Decagon Devices EC-TM sensor measurements. The rainy day effects removal procedure from SWC data was automated by incorporating a statistical inference technique with temperature correction algorithms. The temperature correction method was evaluated using 34 stations from the International Soil Moisture Monitoring Network and another nine stations from a local soil moisture monitoring network in Mongolia. Soil moisture monitoring networks used in this study cover four major climates and six major soil types. Results indicated that the automated temperature correction algorithms developed in this study can eliminate temperature effects from dielectric sensor measurements successfully even without on-site rainfall data. Furthermore, it has been found that actual daily average of SWC has been changed due to temperature effects of dielectric sensors with a

Dielectric properties of DNA oligonucleotides on the surface of silicon nanostructures

Energy Technology Data Exchange (ETDEWEB)

Bagraev, N. T., E-mail: bagraev@mail.ioffe.ru [St. Petersburg Polytechnic University (Russian Federation); Chernev, A. L. [Russian Academy of Sciences, St. Petersburg Academic University—Nanotechnology Research and Education Center (Russian Federation); Klyachkin, L. E. [St. Petersburg Polytechnic University (Russian Federation); Malyarenko, A. M. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Emel’yanov, A. K.; Dubina, M. V. [Russian Academy of Sciences, St. Petersburg Academic University—Nanotechnology Research and Education Center (Russian Federation)

2016-10-15

Planar silicon nanostructures that are formed as a very narrow silicon quantum well confined by δ barriers heavily doped with boron are used to study the dielectric properties of DNA oligonucleotides deposited onto the surface of the nanostructures. The capacitance characteristics of the silicon nanostructures with oligonucleotides deposited onto their surface are determined by recording the local tunneling current–voltage characteristics by means of scanning tunneling microscopy. The results show the possibility of identifying the local dielectric properties of DNA oligonucleotide segments consisting of repeating G–C pairs. These properties apparently give grounds to correlate the segments with polymer molecules exhibiting the properties of multiferroics.

Dielectric loss of strontium titanate thin films

Science.gov (United States)

Dalberth, Mark Joseph

1999-12-01

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

Atomic-scale microstructures, Raman spectra and dielectric properties of cubic pyrochlore-typed Bi1.5MgNb1.5O7 dielectric ceramics

KAUST Repository

Li, Yangyang

2014-07-01

Single-phase cubic pyrochlore-typed Bi1.5MgNb 1.5O7 (BMN) dielectric ceramics were synthesized at temperatures of 1050-1200 °C by solid-state reaction method. Their atomic-scale microstructures and dielectric properties were investigated. X-ray diffraction patterns revealed that the BMN ceramics had an average cubic pyrochlore structure, whereas the Raman spectra indicated that they had an essentially cubic symmetry with small local deviations at the A and O\\' sites of the cubic pyrochlore structure. This was confirmed by selected electron area diffraction (SAED) patterns, where the reflections of {442} (not allowed in the cubic pyrochlore with Fd3̄m symmetry) were clearly observed. SEM and TEM images revealed that the average grain size was increased with the sintering temperature, and an un-homogeneous grain growth was observed at high temperatures. HRTEM images and SAED patterns revealed the single-crystalline nature of the BMN ceramic grains. Energy dispersive spectroscopy (EDS) elemental mapping studies indicated that the compositional distributions of Bi, Mg, Nb and O elements in the ceramic grains were homogenous, and no elemental precipitation was observed at the grain boundary. Quantitative EDS data on ceramic grains revealed the expected cationic stoichiometry based on the initial composition of Bi1.5MgNb1.5O7. Dielectric constants of all the BMN samples exhibited almost frequency independent characteristic in the frequency range of 102-106 Hz, and the highest value was 195 for the BMN ceramics sintered at sintered at 1150 °C with the highest bulk density. The dielectric losses were stable and less than 0.002 in the frequency range of 102-105 Hz. The high dielectric constants of the present BMN samples can be ascribed to the local atomic deviations at the A and O\\' sites from the ideal atomic positions of the pyrochlore structure, which affect the different polarization mechanisms in the BMN ceramics, and which in turn enhance the dielectric

Atomic-scale microstructures, Raman spectra and dielectric properties of cubic pyrochlore-typed Bi1.5MgNb1.5O7 dielectric ceramics

KAUST Repository

Li, Yangyang; Zhu, Xinhua; Al-Kassab, Talaat

2014-01-01

Single-phase cubic pyrochlore-typed Bi1.5MgNb 1.5O7 (BMN) dielectric ceramics were synthesized at temperatures of 1050-1200 °C by solid-state reaction method. Their atomic-scale microstructures and dielectric properties were investigated. X-ray diffraction patterns revealed that the BMN ceramics had an average cubic pyrochlore structure, whereas the Raman spectra indicated that they had an essentially cubic symmetry with small local deviations at the A and O' sites of the cubic pyrochlore structure. This was confirmed by selected electron area diffraction (SAED) patterns, where the reflections of {442} (not allowed in the cubic pyrochlore with Fd3̄m symmetry) were clearly observed. SEM and TEM images revealed that the average grain size was increased with the sintering temperature, and an un-homogeneous grain growth was observed at high temperatures. HRTEM images and SAED patterns revealed the single-crystalline nature of the BMN ceramic grains. Energy dispersive spectroscopy (EDS) elemental mapping studies indicated that the compositional distributions of Bi, Mg, Nb and O elements in the ceramic grains were homogenous, and no elemental precipitation was observed at the grain boundary. Quantitative EDS data on ceramic grains revealed the expected cationic stoichiometry based on the initial composition of Bi1.5MgNb1.5O7. Dielectric constants of all the BMN samples exhibited almost frequency independent characteristic in the frequency range of 102-106 Hz, and the highest value was 195 for the BMN ceramics sintered at sintered at 1150 °C with the highest bulk density. The dielectric losses were stable and less than 0.002 in the frequency range of 102-105 Hz. The high dielectric constants of the present BMN samples can be ascribed to the local atomic deviations at the A and O' sites from the ideal atomic positions of the pyrochlore structure, which affect the different polarization mechanisms in the BMN ceramics, and which in turn enhance the dielectric constants of

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

Institute of Scientific and Technical Information of China (English)

ZHOU Lijun; LI Xianlang; WU Guangning

2013-01-01

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

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

Czech Academy of Sciences Publication Activity Database

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

2015-01-01

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

Histologic response after neoadjuvant chemoradiotherapy in locally ...

African Journals Online (AJOL)

Background: Locally advanced rectal cancer can be down staged by neoadjuvant therapy and the resultant tumor response can be quantified histologically. This study aimed to assess pathological response of neoadjuvant chemoradiation in patients with locally advanced rectal cancers treated in Wad Medani Teaching ...

Modeling non-locality of plasmonic excitations with a fictitious film

Science.gov (United States)

Kong, Jiantao; Shvonski, Alexander; Kempa, Krzysztof

Non-local effects, requiring a wavevector (q) dependent dielectric response are becoming increasingly important in studies of plasmonic and metamaterial structures. The phenomenological hydrodynamic approximation (HDA) is the simplest, and most often used model, but it often fails. We show that the d-function formalism, exact to first order in q, is a powerful and simple-to-use alternative. Recently, we developed a mapping of the d-function formalism into a purely local fictitious film. This geometric mapping allows for non-local extensions of any local calculation scheme, including FDTD. We demonstrate here, that such mapped FDTD simulation of metallic nanoclusters agrees very well with various experiments.

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

Czech Academy of Sciences Publication Activity Database

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

2008-01-01

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

Functional silicone copolymers and elastomers with high dielectric permittivity

DEFF Research Database (Denmark)

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

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

Dielectric metasurfaces solve differential and integro-differential equations.

Science.gov (United States)

Abdollahramezani, Sajjad; Chizari, Ata; Dorche, Ali Eshaghian; Jamali, Mohammad Vahid; Salehi, Jawad A

2017-04-01

Leveraging subwavelength resonant nanostructures, plasmonic metasurfaces have recently attracted much attention as a breakthrough concept for engineering optical waves both spatially and spectrally. However, inherent ohmic losses concomitant with low coupling efficiencies pose fundamental impediments over their practical applications. Not only can all-dielectric metasurfaces tackle such substantial drawbacks, but also their CMOS-compatible configurations support both Mie resonances that are invariant to the incident angle. Here, we report on a transmittive metasurface comprising arrayed silicon nanodisks embedded in a homogeneous dielectric medium to manipulate phase and amplitude of incident light locally and almost independently. By taking advantage of the interplay between the electric/magnetic resonances and employing general concepts of spatial Fourier transformation, a highly efficient metadevice is proposed to perform mathematical operations including solution of ordinary differential and integro-differential equations with constant coefficients. Our findings further substantiate dielectric metasurfaces as promising candidates for miniaturized, two-dimensional, and planar optical analog computing systems that are much thinner than their conventional lens-based counterparts.

Influence of particle surface properties on the dielectric behavior of silica/epoxy nanocomposites

International Nuclear Information System (INIS)

Cheng Lihong; Zheng Liaoying; Li Guorong; Zeng Jiangtao; Yin Qingrui

2008-01-01

Silica/epoxy composites have been widely used in functional electric device applications. Silica nanoparticles, both unmodified and modified with the coupling agent KH-550, were used to prepare epoxy composites. Dielectric measurements showed that nanocomposites exhibit a higher dielectric constant than the control sample, and had more obvious dielectric relaxation characteristics. Results showed that particle surface properties have a profound effect on the dielectric behavior of the nanocomposites. These characteristics are attributed to the local ununiformity of the microstructure caused by the large interface area and the interaction between the filler and the matrix. This phenomenon is explained in terms of prolonging chemical chains created during the curing process. The mechanism is discussed with measurements of X-ray diffraction (XRD) and Fourier transform infrared (FTIR)

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

Czech Academy of Sciences Publication Activity Database

Mokrý, Pavel; Sluka, T.

2016-01-01

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

Research of Steel-dielectric Transition Using Subminiature Eddy-current Transducer

Science.gov (United States)

Dmitriev, S. F.; Malikov, V. N.; Sagalakov, A. M.; Ishkov, A. V.

2018-05-01

The research aims to develop a subminiature transducer for electrical steel investigation. The authors determined the capability to study steel characteristics at different depths based on variations of eddy-current transducer amplitude at the steel-dielectric boundary. A subminiature transformer-type transducer was designed, which enables to perform local investigations of ferromagnetic materials using an eddy-current method based on local studies of the steel electrical conductivity. Having the designed transducer as a basis, a hardware-software complex was built to perform experimental studies of steel at the interface boundary. Test results are reported for a specimen with continuous and discrete measurements taken at different frequencies. The article provides the key technical information about the eddy current transformer used and describes the methodology of measurements that makes it possible to control steel to dielectric transition.

Fault Management of a Cold Dielectric HTS Power Transmission Cable

International Nuclear Information System (INIS)

Maguire, J; Allais, A; Yuan, J; Schmidt, F; Hamber, F; Welsh, Tom

2006-01-01

High temperature superconductor (HTS) power transmission cables offer significant advantages in power density over conventional copper-based cables. As with conventional cables, HTS cables must be safe and reliable when abnormal conditions, such as local and through faults, occur in the power grid. Due to the unique characteristics of HTS power cables, the fault management of an HTS cable is different from that of a conventional cable. Issues, such as nitrogen bubble formation within lapped dielectric material, need to be addressed. This paper reviews the efforts that have been performed to study the fault conditions of a cold dielectric HTS power cable. As a result of the efforts, a fault management scheme has been developed, which provides both local and through faults system protection. Details of the fault management scheme with examples are presented

Virtual gap dielectric wall accelerator

Science.gov (United States)

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

2013-11-05

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

Dielectric and baric characteristics of TlS single crystal

Energy Technology Data Exchange (ETDEWEB)

Mustafaeva, S.N., E-mail: solmust@gmail.com [Institute of Physics, ANAS, G. Javid prosp. 33, Az 1143 Baku (Azerbaijan); Asadov, M.M. [Institute of Chemical Problems, ANAS, G. Javid prosp. 29, Az 1143 Baku (Azerbaijan); Ismailov, A.A. [Institute of Physics, ANAS, G. Javid prosp. 33, Az 1143 Baku (Azerbaijan)

2014-11-15

The investigation of the frequency dependences of the dielectric coefficients and ac-conductivity of the TlS single crystals made it possible to elucidate the nature of dielectric loss and the charge transfer mechanism. Moreover, we evaluated the density and energy spread of localized states near the Fermi level, the average hopping time and the average hopping length. It was shown that the dc-conductivity of the TlS single crystals can be controlled by varying the hydrostatic pressure. This has opened up possibilities for using TlS single crystals as active elements of pressure detectors.

Boron nitride as two dimensional dielectric: Reliability and dielectric breakdown

Energy Technology Data Exchange (ETDEWEB)

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

2016-01-04

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

Lattices of dielectric resonators

CERN Document Server

Trubin, Alexander

2016-01-01

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

Band structure and dielectric function of TlInTe2

International Nuclear Information System (INIS)

Wakita, K.; Shim, Y.; Orudzhev, G.; Mamedov, N.; Hashimzade, F.

2006-01-01

The band structure of ternary chain TlInTe 2 was calculated with allowance for non-locality of ionic pseudo-potentials. The dielectric function, as well as the effective masses of holes and electrons, the effective number of valence electrons, and the function of characteristic losses were determined. The results of comparison between the calculated dielectric function and the one obtained ellipsometrically in the spectral range from 0.85 to 6 eV are quite favorable. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2006], Wiley Periodicals, Inc.)

Dielectric spectroscopy as a sensor of membrane headgroup mobility and hydration

DEFF Research Database (Denmark)

Klösgen, B; Reichle, C; Kohlsmann, S

1996-01-01

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

Influence of color on dielectric properties of marinated poultry breast meat.

Science.gov (United States)

Samuel, D; Trabelsi, S

2012-08-01

The dielectric behavior of foods when exposed to radio-frequency and microwave electric fields is highly influenced by moisture content and the degree of water binding with constituents of the food materials. The ability to correlate specific food quality characteristics with the dielectric properties can lead to the development of rapid, nondestructive techniques for such quality measurements. Water-holding capacity is a critical attribute in meat quality. Up to 50% of raw poultry meat in the United States is marinated with mixtures of water, salts, and phosphates. The objective of this study was to determine if variations in breast meat color would affect the dielectric properties of marinated poultry meat over a broad frequency range from 500 MHz to 50 GHz. Poultry meat was obtained from a local commercial plant in Georgia (USA). Color and pH measurements were taken on the breast filets. Groups of breast filets were sorted into classes of pale and normal before adding marination pickup percentages of 0, 5, 10, and 15. Breast filets were vacuum-tumbled and weighed for pickup percentages. Dielectric properties of the filets were measured with a coaxial open-ended probe on samples equilibrated to 25°C. Samples from pale meat exhibited higher dielectric properties than samples from normal meat. No differences could be observed between samples from pale and normal meat after marination of the samples. Overall, dielectric properties increased as the marination pickup increased (α=0.05). Marination pickup strongly influenced the dielectric loss factor. Differences between samples marinated at different pickup levels were more pronounced at lower frequencies for the dielectric loss factor. As frequency increased, the differences between samples decreased. Differences in dielectric constant between samples were not as consistent as those seen with the dielectric loss factor.

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

Science.gov (United States)

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

2014-06-10

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

Efficient Algorithms for Electrostatic Interactions Including Dielectric Contrasts

Directory of Open Access Journals (Sweden)

Christian Holm

2013-10-01

Full Text Available Coarse-grained models of soft matter are usually combined with implicit solvent models that take the electrostatic polarizability into account via a dielectric background. In biophysical or nanoscale simulations that include water, this constant can vary greatly within the system. Performing molecular dynamics or other simulations that need to compute exact electrostatic interactions between charges in those systems is computationally demanding. We review here several algorithms developed by us that perform exactly this task. For planar dielectric surfaces in partial periodic boundary conditions, the arising image charges can be either treated with the MMM2D algorithm in a very efficient and accurate way or with the electrostatic layer correction term, which enables the user to use his favorite 3D periodic Coulomb solver. Arbitrarily-shaped interfaces can be dealt with using induced surface charges with the induced charge calculation (ICC* algorithm. Finally, the local electrostatics algorithm, MEMD(Maxwell Equations Molecular Dynamics, even allows one to employ a smoothly varying dielectric constant in the systems. We introduce the concepts of these three algorithms and an extension for the inclusion of boundaries that are to be held fixed at a constant potential (metal conditions. For each method, we present a showcase application to highlight the importance of dielectric interfaces.

Microstructure and chemical analysis of Hf-based high-k dielectric layers in metal-insulator-metal capacitors

Energy Technology Data Exchange (ETDEWEB)

Thangadurai, P. [Department of Materials Engineering, Technion - Israel Institute of Technology, Haifa 32000 (Israel); Mikhelashvili, V.; Eisenstein, G. [Department of Electrical Engineering, Technion - Israel Institute of Technology, Haifa 32000 (Israel); Kaplan, W.D., E-mail: kaplan@tx.technion.ac.i [Department of Materials Engineering, Technion - Israel Institute of Technology, Haifa 32000 (Israel)

2010-05-31

The microstructure and chemistry of the high-k gate dielectric significantly influences the performance of metal-insulator-metal (MIM) and metal-oxide-semiconductor devices. In particular, the local structure, chemistry, and inter-layer mixing are important phenomena to be understood. In the present study, high resolution and analytical transmission electron microscopy are combined to study the local structure, morphology, and chemistry in MIM capacitors containing a Hf-based high-k dielectric. The gate dielectric, bottom and gate electrodes were deposited on p-type Si(100) wafers by electron beam evaporation. Four chemically distinguishable sub-layers were identified within the dielectric stack. One is an unintentionally formed 4.0 nm thick interfacial layer of Ta{sub 2}O{sub 5} at the interface between the Ta electrode and the dielectric. The other three layers are based on HfN{sub x}O{sub y} and HfTiO{sub y}, and intermixing between the nearby sub-layers including deposited SiO{sub 2}. Hf-rich clusters were found in the HfN{sub x}O{sub y} layer adjacent to the Ta{sub 2}O{sub 5} layer.

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

DEFF Research Database (Denmark)

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

2016-01-01

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

Dielectrics in electric fields

CERN Document Server

Raju, Gorur G

2003-01-01

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

Flexible non-diffractive vortex microscope for three-dimensional depth-enhanced super-localization of dielectric, metal and fluorescent nanoparticles

Science.gov (United States)

Bouchal, Petr; Bouchal, Zdeněk

2017-10-01

In the past decade, probe-based super-resolution using temporally resolved localization of emitters became a groundbreaking imaging strategy in fluorescence microscopy. Here we demonstrate a non-diffractive vortex microscope (NVM), enabling three-dimensional super-resolution fluorescence imaging and localization and tracking of metal and dielectric nanoparticles. The NVM benefits from vortex non-diffractive beams (NBs) creating a double-helix point spread function that rotates under defocusing while maintaining its size and shape unchanged. Using intrinsic properties of the NBs, the dark-field localization of weakly scattering objects is achieved in a large axial range exceeding the depth of field of the microscope objective up to 23 times. The NVM was developed using an upright microscope Nikon Eclipse E600 operating with a spiral lithographic mask optimized using Fisher information and built into an add-on imaging module or microscope objective. In evaluation of the axial localization accuracy the root mean square error below 18 nm and 280 nm was verified over depth ranges of 3.5 μm and 13.6 μm, respectively. Subwavelength gold and polystyrene beads were localized with isotropic precision below 10 nm in the axial range of 3.5 μm and the axial precision reduced to 30 nm in the extended range of 13.6 μm. In the fluorescence imaging, the localization with isotropic precision below 15 nm was demonstrated in the range of 2.5 μm, whereas in the range of 8.3 μm, the precision of 15 nm laterally and 30-50 nm axially was achieved. The tracking of nanoparticles undergoing Brownian motion was demonstrated in the volume of 14 × 10 × 16 μm3. Applicability of the NVM was tested by fluorescence imaging of LW13K2 cells and localization of cellular proteins.

Inductive dielectric analyzer

International Nuclear Information System (INIS)

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

2017-01-01

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

Finite element analysis and validation of dielectric elastomer actuators used for active origami

International Nuclear Information System (INIS)

McGough, Kevin; Ahmed, Saad; Frecker, Mary; Ounaies, Zoubeida

2014-01-01

The field of active origami explores the incorporation of active materials into origami-inspired structures in order to serve as a means of actuation. Active origami-inspired structures capable of folding into complex three-dimensional (3D) shapes have the potential to be lightweight and versatile compared to traditional methods of actuation. This paper details the finite element analysis and experimental validation of unimorph actuators. Actuators are fabricated by adhering layers of electroded dielectric elastomer (3M VHB F9473PC) onto a passive substrate layer (3M Magic Scotch Tape). Finite element analysis of the actuators simulates the electromechanical coupling of the dielectric elastomer under an applied voltage by applying pressures to the surfaces of the dielectric elastomer where the compliant electrode (conductive carbon grease) is present. 3D finite element analysis of the bending actuators shows that applying contact boundary conditions to the electroded region of the active and passive layers provides better agreement to experimental data compared to modeling the entire actuator as continuous. To improve the applicability of dielectric elastomer-based actuators for active origami-inspired structures, folding actuators are developed by taking advantage of localized deformation caused by a passive layer with non-uniform thickness. Two-dimensional analysis of the folding actuators shows that agreement to experimental data diminishes as localized deformation increases. Limitations of using pressures to approximate the electromechanical coupling of the dielectric elastomer under an applied electric field and additional modeling considerations are also discussed. (paper)

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

Science.gov (United States)

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

2016-05-01

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

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

KAUST Repository

Khan, Kamran

2012-11-10

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

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

Directory of Open Access Journals (Sweden)

H. A. E. Malhat

2015-02-01

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

Inertial polarization of dielectrics

OpenAIRE

Zavodovsky, A. G.

2011-01-01

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

Localized plasmons in graphene-coated nanospheres

DEFF Research Database (Denmark)

Christensen, Thomas; Jauho, Antti-Pekka; Wubs, Martijn

2015-01-01

We present an analytical derivation of the electromagnetic response of a spherical object coated by a conductive film, here exemplified by a graphene coating. Applying the framework of Mie-Lorenz theory augmented to account for a conductive boundary condition, we derive the multipole scattering...... for the localized plasmons. We consider graphene coatings of both dielectric and conducting spheres, where the graphene coating in the former case introduces the plasmons and in the latter case modifies in interesting ways the existing ones. Finally, we discuss our analytical results in the context of extinction...

Interaction of metallic nanoparticles with dielectric substrates: effect of optical constants

International Nuclear Information System (INIS)

Hutter, Tanya; Elliott, Stephen R; Mahajan, Sumeet

2013-01-01

In this paper, we study the local-field enhancement in a system of a metallic nanoparticle placed very near to a dielectric substrate. In such systems, intense electric fields are localized in the gap between the particle and the substrate, creating a ‘hot-spot’ under appropriate excitation conditions. We use finite-element numerical simulations in order to study the field enhancement in this dielectric–metal system. More specifically, we show how the optical properties of the dielectric substrate (n and k) affect the plasmonic field enhancement in the nano-gap. We also analyze the degree of field confinement in the gap and discuss it in the context of utilization for surface-enhanced Raman scattering. We finally show the fields generated by real substrates and compare them to metallic ones. (paper)

Dielectric materials for electrical engineering

CERN Document Server

Martinez-Vega, Juan

2013-01-01

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

Cast dielectric composite linear accelerator

Science.gov (United States)

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

2009-11-10

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

Vertical dielectric screening of few-layer van der Waals semiconductors.

Science.gov (United States)

Koo, Jahyun; Gao, Shiyuan; Lee, Hoonkyung; Yang, Li

2017-10-05

Vertical dielectric screening is a fundamental parameter of few-layer van der Waals two-dimensional (2D) semiconductors. However, unlike the widely-accepted wisdom claiming that the vertical dielectric screening is sensitive to the thickness, our first-principles calculation based on the linear response theory (within the weak field limit) reveals that this screening is independent of the thickness and, in fact, it is the same as the corresponding bulk value. This conclusion is verified in a wide range of 2D paraelectric semiconductors, covering narrow-gap ones and wide-gap ones with different crystal symmetries, providing an efficient and reliable way to calculate and predict static dielectric screening of reduced-dimensional materials. Employing this conclusion, we satisfactorily explain the tunable band gap in gated 2D semiconductors. We further propose to engineer the vertical dielectric screening by changing the interlayer distance via vertical pressure or hybrid structures. Our predicted vertical dielectric screening can substantially simplify the understanding of a wide range of measurements and it is crucial for designing 2D functional devices.

Improved Dielectric Films For Capacitors

Science.gov (United States)

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

1994-01-01

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

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

Science.gov (United States)

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

2016-10-21

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

Ceramic-polymer nanocomposites with increased dielectric permittivity and low dielectric loss

International Nuclear Information System (INIS)

Bhardwaj, Sumit; Paul, Joginder; Raina, K. K.; Thakur, N. S.; Kumar, Ravi

2014-01-01

The use of lead free materials in device fabrication is very essential from environmental point of view. We have synthesized the lead free ferroelectric polymer nanocomposite films with increased dielectric properties. Lead free bismuth titanate has been used as active ceramic nanofillers having crystallite size 24nm and PVDF as the polymer matrix. Ferroelectric β-phase of the polymer composite films was confirmed by X-ray diffraction pattern. Mapping data confirms the homogeneous dispersion of ceramic particles into the polymer matrix. Frequency dependent dielectric constant increases up to 43.4 at 100Hz, whereas dielectric loss decreases with 7 wt% bismuth titanate loading. This high dielectric constant lead free ferroelectric polymer films can be used for energy density applications

Metal-in-metal localized surface plasmon resonance

Energy Technology Data Exchange (ETDEWEB)

Smith, G B; Earp, A A, E-mail: g.smith@uts.edu.au [Department of Physics and Advanced Materials and Institute of Nanoscale Technology, University of Technology, Sydney, PO Box 123, Broadway NSW 2007 (Australia)

2010-01-08

Anomalous strong resonances in silver and gold nanoporous thin films which conduct are found to arise from isolated metal nano-islands separated from the surrounding percolating metal network by a thin loop of insulator. This observed resonant optical response is modelled. The observed peak position is in agreement with the observed average dimensions of the silver core and insulator shell. As the insulating ring thickness shrinks, the resonance moves to longer wavelengths and strengthens. This structure is the Babinet's principle counterpart of dielectric core-metal shell nanoparticles embedded in dielectric. Like for the latter, tuning of resonant absorption is possible, but here the matrix reflects rather than transmits, and tuning to longer wavelengths is more practical. A new class of metal mirror occurring as a single thin layer is identified using the same resonances in dense metal mirrors. Narrow band deep localized dips in reflectance result.

Metal-in-metal localized surface plasmon resonance

Science.gov (United States)

Smith, G. B.; Earp, A. A.

2010-01-01

Anomalous strong resonances in silver and gold nanoporous thin films which conduct are found to arise from isolated metal nano-islands separated from the surrounding percolating metal network by a thin loop of insulator. This observed resonant optical response is modelled. The observed peak position is in agreement with the observed average dimensions of the silver core and insulator shell. As the insulating ring thickness shrinks, the resonance moves to longer wavelengths and strengthens. This structure is the Babinet's principle counterpart of dielectric core-metal shell nanoparticles embedded in dielectric. Like for the latter, tuning of resonant absorption is possible, but here the matrix reflects rather than transmits, and tuning to longer wavelengths is more practical. A new class of metal mirror occurring as a single thin layer is identified using the same resonances in dense metal mirrors. Narrow band deep localized dips in reflectance result.

Dielectric and impedance spectral characteristics of bulk ZnIn2Se4

Science.gov (United States)

El-Nahass, M. M.; Attia, A. A.; Salem, G. F.; Ali, H. A. M.; Ismail, M. I.

2014-02-01

The frequency and temperature dependence of ac conductivity, dielectric constant and dielectric loss of ZnIn2Se4 in a pellet form were investigated in the frequency range of 102-106 Hz and temperature range of 293-356 K. The behavior of ac conductivity was interpreted by the correlated barrier hopping (CBH) model. Temperature dependence of ac conductivity indicates that ac conduction is a thermally activated process. The density of localized states N(EF) and ac activation energy were estimated for various frequencies. Dielectric constant and dielectric loss showed a decrease with increasing frequency and an increase with increasing in temperature. The frequency dependence of real and imaginary parts of the complex impedance was investigated. The relaxation time decreases with the increase in temperature. The impedance spectrum exhibits the appearance of the single semicircular arc. The radius of semicircular arcs decreases with increasing temperature which suggests a mechanism of temperature-dependent on relaxation.

Local Development Responses in Zambia:The Case of Kitwe ...

African Journals Online (AJOL)

growth in planning initiatives for Local Economic Development (LED). This article examines LED activities in the city of Kitwe, against the backdrop of regional and local economic decline, two different sets of responses may be recognised: (i) local government led initiatives and (ii) 'bottom up' LED responses arising from the ...

On the nature of high field charge transport in reinforced silicone dielectrics: Experiment and simulation

Energy Technology Data Exchange (ETDEWEB)

Huang, Yanhui, E-mail: huangy12@rpi.edu; Schadler, Linda S. [Department of Material Science and Engineering, Rensselaer Polytechnic Institute, 110 8th street, Troy, New York 12180 (United States)

2016-08-07

The high field charge injection and transport properties in reinforced silicone dielectrics were investigated by measuring the time-dependent space charge distribution and the current under dc conditions up to the breakdown field and were compared with the properties of other dielectric polymers. It is argued that the energy and spatial distribution of localized electronic states are crucial in determining these properties for polymer dielectrics. Tunneling to localized states likely dominates the charge injection process. A transient transport regime arises due to the relaxation of charge carriers into deep traps at the energy band tails and is successfully verified by a Monte Carlo simulation using the multiple-hopping model. The charge carrier mobility is found to be highly heterogeneous due to the non-uniform trapping. The slow moving electron packet exhibits a negative field dependent drift velocity possibly due to the spatial disorder of traps.

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Time domain PD-detection vs. dielectric spectroscopy

DEFF Research Database (Denmark)

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

1997-01-01

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

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

International Nuclear Information System (INIS)

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

2013-01-01

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

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

Science.gov (United States)

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

2016-01-01

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

Localized surface plasmon enhanced deep UV-emitting of AlGaN based multi-quantum wells by Al nanoparticles on SiO2 dielectric interlayer

Science.gov (United States)

He, Ju; Wang, Shuai; Chen, Jingwen; Wu, Feng; Dai, Jiangnan; Long, Hanling; Zhang, Yi; Zhang, Wei; Feng, Zhe Chuan; Zhang, Jun; Du, Shida; Ye, Lei; Chen, Changqing

2018-05-01

In this paper, we report a 2.6-fold deep ultraviolet emission enhancement of integrated photoluminescence (PL) intensity in AlGaN-based multi-quantum wells (MQWs) by introducing the coupling of local surface plasmons from Al nanoparticles (NPs) on a SiO2 dielectric interlayer with excitons and photons in MQWs at room temperature. In comparison to bare AlGaN MQWs, a significant 2.3-fold enhancement of the internal quantum efficiency, from 16% to 37%, as well as a 13% enhancement of photon extraction efficiency have been observed in the MQWs decorated with Al NPs on SiO2 dielectric interlayer. Polarization-dependent PL measurement showed that both the transverse electric and transverse magnetic mode were stronger than the original intensity in bare AlGaN MQWs, indicating a strong LSPs coupling process and vigorous scattering ability of the Al/SiO2 composite structure. These results were confirmed by the activation energy of non-radiative recombination from temperature-dependent PL measurement and the theoretical three dimensional finite difference time domain calculations.

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

Science.gov (United States)

2012-10-24

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

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

Directory of Open Access Journals (Sweden)

Shijiao Han

2016-10-01

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

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

Science.gov (United States)

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

2016-01-01

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

Optimal Super Dielectric Material

Science.gov (United States)

2015-09-01

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

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

Science.gov (United States)

Cordero, F.

2018-03-01

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

Self Oscillating Mixer with Dielectric Resonator for Low Noise Block Application

Directory of Open Access Journals (Sweden)

Endon Bharata

2011-08-01

Full Text Available In this paper, the development of a self oscillating mixer (SOM as part of a low noise block (LNB for a satellite television receiver is investigated numerically and experimentally. In contrast to other mixers, the developed SOM requires no separate local oscillator as it generates own local oscillator signal. The SOM is developed using a monolithic microwave integrated circuit (MMIC comprised of two bipolar transistors coupled as a Darlington pair and a dielectric resonator to establish a local oscillator signal. The SOM is designed to oscillate at 3.62GHz driven from 50W signal generator. The prototype of SOM is fabricated on a dielectric substrate of glass-reinforced hydrocarbon/ceramic lamination (RO4350B board which has a thickness of 0.762mm and relative permittivity of 3.66. The prototype is then characterized experimentally and exhibits a conversion gain of 8dB with the input and output voltage standing wave ratio (VSWR less than 2 across the 2520MHz to 2670MHz operating frequency band.

Dielectric response of KCN crystals at ultra-low frequencies

OpenAIRE

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

1987-01-01

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

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

Directory of Open Access Journals (Sweden)

Medeiros Jamilson Pinto

1998-01-01

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

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

International Nuclear Information System (INIS)

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

2008-01-01

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

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

Science.gov (United States)

Saini, Abhishek; Ahmad, Dilshad; Patra, Karali

2016-04-01

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

Performance of dielectric nanocomposites: matrix-free, hairy nanoparticle assemblies and amorphous polymer-nanoparticle blends.

Science.gov (United States)

Grabowski, Christopher A; Koerner, Hilmar; Meth, Jeffrey S; Dang, Alei; Hui, Chin Ming; Matyjaszewski, Krzysztof; Bockstaller, Michael R; Durstock, Michael F; Vaia, Richard A

2014-12-10

Demands to increase the stored energy density of electrostatic capacitors have spurred the development of materials with enhanced dielectric breakdown, improved permittivity, and reduced dielectric loss. Polymer nanocomposites (PNCs), consisting of a blend of amorphous polymer and dielectric nanofillers, have been studied intensely to satisfy these goals; however, nanoparticle aggregates, field localization due to dielectric mismatch between particle and matrix, and the poorly understood role of interface compatibilization have challenged progress. To expand the understanding of the inter-relation between these factors and, thus, enable rational optimization of low and high contrast PNC dielectrics, we compare the dielectric performance of matrix-free hairy nanoparticle assemblies (aHNPs) to blended PNCs in the regime of low dielectric contrast to establish how morphology and interface impact energy storage and breakdown across different polymer matrices (polystyrene, PS, and poly(methyl methacrylate), PMMA) and nanoparticle loadings (0-50% (v/v) silica). The findings indicate that the route (aHNP versus blending) to well-dispersed morphology has, at most, a minor impact on breakdown strength trends with nanoparticle volume fraction; the only exception being at intermediate loadings of silica in PMMA (15% (v/v)). Conversely, aHNPs show substantial improvements in reducing dielectric loss and maintaining charge/discharge efficiency. For example, low-frequency dielectric loss (1 Hz-1 kHz) of PS and PMMA aHNP films was essentially unchanged up to a silica content of 50% (v/v), whereas traditional blends showed a monotonically increasing loss with silica loading. Similar benefits are seen via high-field polarization loop measurements where energy storage for ∼15% (v/v) silica loaded PMMA and PS aHNPs were 50% and 200% greater than respective comparable PNC blends. Overall, these findings on low dielectric contrast PNCs clearly point to the performance benefits of

PREFACE: Dielectrics 2009: Measurement Analysis and Applications

Science.gov (United States)

Vaughan, Alun; Williams, Graham

2009-07-01

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

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

Science.gov (United States)

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

1998-03-01

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

Scaling parallels in the non-Debye dielectric relaxation of ionic glasses and dipolar supercooled liquids

International Nuclear Information System (INIS)

Sidebottom, D.L.; Green, P.F.; Brow, R.K.

1997-01-01

We compare the dielectric response of ionic glasses and dipolar liquids near the glass transition. Our work is divided into two parts. In the first section we examine ionic glasses and the two prominent approaches to analyzing the dielectric response. The conductivity of ion-conducting glasses displays a power law dispersion σ(ω)∝ω n , where n∼0.67, but frequently the dielectric response is analyzed using the electrical modulus M * (ω)=1/var-epsilon * (ω), where var-epsilon * (ω)=var-epsilon(ω)-iσ(ω)/ω is the complex permittivity. We reexamine two specific examples where the shape of M * (ω) changes in response to changes in (a) temperature and (b) ion concentration, to suggest fundamental changes in ion dynamics are occurring. We show, however, that these changes in the shape of M * (ω) occur in the absence of changes in the scaling properties of σ(ω), for which n remains constant. In the second part, we examine the dielectric relaxation found in dipolar liquids, for which var-epsilon * (ω) likewise exhibits changes in shape on approach to the glass transition. Guided by similarities of M * (ω) in ionic glasses and var-epsilon * (ω) in dipolar liquids, we demonstrate that a recent scaling approach proposed by Dixon and co-workers for var-epsilon * (ω) of dipolar relaxation also appears valid for M * (ω) in the ionic case. While this suggests that the Dixon scaling approach is more universal than previously recognized, we demonstrate how the dielectric response can be scaled in a linear manner using an alternative data representation. copyright 1997 The American Physical Society

Dielectric Losses and Charge Transfer in Antimony-Doped TlGaS2 Single Crystal

Science.gov (United States)

Asadov, S. M.; Mustafaeva, S. N.

2018-03-01

Effect of semimetallic antimony (0.5 mol % Sb) on the dielectric properties and ac-conductivity of TlGaS2-based single crystals grown by the Bridgman-Stockbarger method has been studied. The experimental results on the frequency dispersion of dielectric coefficients and the conductivity of TlGa0.995Sb0.005S2 single crystals allowed the revealing of the dielectric loss nature, the charge transfer mechanism, and the estimation of the parameters of the states localized in the energy gap. The antimony-doping of the TlGaS2 single crystal leads to an increase in the density of states near the Fermi level and a decrease in the average time and average distance of hopes.

Tuneabilities of localized electromagnetic modes in random nanostructures for random lasing

Science.gov (United States)

Takeda, S.; Obara, M.

2010-02-01

The modal characteristics of localized electromagnetic waves inside random nanostructures are theoretically presented. It is crucial to know the tuneabilities of the localized modes systematically for demonstrating a specific random lasing application. By use of FDTD (Finite-Difference Time-Domain) method, we investigated the impulse response of two-dimensional random nanostructures consisting of closely packed cylindrical dielectric columns, and precisely analyzed the localized modes. We revealed the tuneability of the frequency of the localized modes by controlling the medium configurations: diameter, spatial density, and refractive index of the cylinders. Furthermore, it is found to be able to tune the Q (quality) factors of the localized modes dramatically by controlling simply the system size of the entire medium. The observed Q factors of approximately 1.6×104 were exhibited in our random disordered structures.

Polarization-induced transport in organic field-effect transistors: the role of ferroelectric dielectrics

Science.gov (United States)

Guha, Suchismita; Laudari, Amrit

2017-08-01

The ferroelectric nature of polymer ferroelectrics such as poly(vinylidene fluoride) (PVDF) has been known for over 45 years. However, its role in interfacial transport in organic/polymeric field-effect transistors (FETs) is not that well understood. Dielectrics based on PVDF and its copolymers are a perfect test-bed for conducting transport studies where a systematic tuning of the dielectric constant with temperature may be achieved. The charge transport mechanism in an organic semiconductor often occurs at the intersection of band-like coherent motion and incoherent hopping through localized states. By choosing two small molecule organic semiconductors - pentacene and 6,13 bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) - along with a copolymer of PVDF (PVDF-TrFe) as the dielectric layer, the transistor characteristics are monitored as a function of temperature. A negative coefficient of carrier mobility is observed in TIPS-pentacene upwards of 200 K with the ferroelectric dielectric. In contrast, TIPS-pentacene FETs show an activated transport with non-ferroelectric dielectrics. Pentacene FETs, on the other hand, show a weak temperature dependence of the charge carrier mobility in the ferroelectric phase of PVDF-TrFE, which is attributed to polarization fluctuation driven transport resulting from a coupling of the charge carriers to the surface phonons of the dielectric layer. Further, we show that there is a strong correlation between the nature of traps in the organic semiconductor and interfacial transport in organic FETs, especially in the presence of a ferroelectric dielectric.

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

Directory of Open Access Journals (Sweden)

D. A. Robinson

1998-01-01

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

Validity and interobserver agreement of lower extremity local tissue water measurements in healthy women using tissue dielectric constant

DEFF Research Database (Denmark)

Jensen, Mads R; Birkballe, Susanne; Nørregaard, Susan

2012-01-01

Tissue dielectric constant (TDC) measurement may become an important tool in the clinical evaluation of chronic lower extremity swelling in women; however, several factors are known to influence TDC measurements, and comparative data on healthy lower extremities are few.......Tissue dielectric constant (TDC) measurement may become an important tool in the clinical evaluation of chronic lower extremity swelling in women; however, several factors are known to influence TDC measurements, and comparative data on healthy lower extremities are few....

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

DEFF Research Database (Denmark)

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

2015-01-01

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

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

DEFF Research Database (Denmark)

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

2014-01-01

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

Dielectric relaxation in Li2SO4 in the intermedia-temperature regime

Science.gov (United States)

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-.

Functional metasurfaces based on metallic and dielectric subwavelength slits and stripes array

Science.gov (United States)

Guo, Yinghui; Pu, Mingbo; Li, Xiong; Ma, Xiaoliang; Gao, Ping; Wang, Yanqin; Luo, Xiangang

2018-04-01

Starting with the early works of extraordinary optical transmission and extraordinary Young’s interference, researchers have been fascinated by the unusual optical properties displayed by metallic holes/slits and subsequently found similar abnormities in dielectric counterparts. Benefiting from the shrinking wavelength of surface plasmon polaritons excited in metallic slits and high refractive index of dielectric stripes, one can realize local phase modulation and approach desired dispersion by engineering the geometries of a slits and stripes array. In this review, we review recent developments in functional metasurfaces composed of various metallic and dielectric subwavelength slits and stripes arrays, with special emphasis on achromatic, ultra-broadband, quasi-continuous, multifunctional and reconfigurable metasurfaces. Particular attention is paid to provide insight into the design strategies for these devices. Finally, we give an outlook of the development in this fascinating area.

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

Energy Technology Data Exchange (ETDEWEB)

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

1994-10-01

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

Dielectric and electrical conductivity studies of bulk lead (II) oxide (PbO)

Energy Technology Data Exchange (ETDEWEB)

Darwish, A.A.A., E-mail: aaadarwish@gmail.com [Department of Physics, Faculty of Education at Al-Mahweet, Sana’a University, Al-Mahwit (Yemen); Department of Physics, Faculty of Science, University of Tabuk, P.O. Box 741, Tabuk 71491, Tabuk (Saudi Arabia); El-Zaidia, E.F.M.; El-Nahass, M.M. [Department of Physics, Faculty of Education, Ain Shams University, Rorxy, Cairo 11757 (Egypt); Hanafy, T.A. [Department of Physics, Faculty of Science, University of Tabuk, P.O. Box 741, Tabuk 71491, Tabuk (Saudi Arabia); Department of Physics, Faculty of Science, Fayoum University, 63514 El Fayoum (Egypt); Al-Zubaidi, A.A. [Department of Physics, Faculty of Science, University of Tabuk, P.O. Box 741, Tabuk 71491, Tabuk (Saudi Arabia)

2014-03-15

Highlights: • The AC measurements of PbO were measured at temperature range 313–523 K. • The dielectric constants increased with temperature. • The mechanism responsible for AC conduction is electronic hopping. -- Abstract: The dielectric properties, the impedance spectroscopy and AC conductivity of bulk PbO have been investigated as a function of frequency and temperature. The measurements were carried out in the frequency range from 40 to 5 × 10{sup 6} Hz and in temperature range from 313 to 523 K. The frequency response of dielectric constant, ε{sub 1}, and dielectric loss index, ε{sub 2}, as a function of temperature were studied. The values of ε{sub 1} and ε{sub 2} were found to decrease with the increase in frequency. However, they increase with the increase in temperature. The presence of a single arc in the complex modulus spectrum at different temperatures confirms the single-phase character of the PbO. The AC conductivity exhibited a universal dynamic response: σ{sub AC} = Aω{sup s}. The AC conductivity was also found to increase with increasing temperature and frequency. The correlation barrier hopping (CBH) model was found to apply to the AC conductivity data. The calculated values of s were decreased with temperature. This behavior reveals that the conduction mechanism for PbO samples is CBH. The activation energy for AC conductivity decreases with increasing frequency. This confirms that the hopping conduction to the dominant mechanism for PbO samples.

Dielectric Properties of PE/Clay Nanocomposites

Directory of Open Access Journals (Sweden)

E. David

2013-01-01

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

Super Dielectric Materials.

Science.gov (United States)

Fromille, Samuel; Phillips, Jonathan

2014-12-22

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

Structural, photoconductivity, and dielectric studies of polythiophene-tin oxide nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Murugavel, S., E-mail: starin85@gmail.com; Malathi, M., E-mail: mmalathi@vit.ac.in

2016-09-15

Highlights: • Synthesis of polythiophene-tin oxide nanocomposites confirmed by FTIR and EDAX. • SEM shows SnO{sub 2} nanoparticles embedded within polythiophene matrix. • Stability and isoelectric point suggest nanoparticle–matrix interaction. • High dielectric constant due to high Maxwell–Wagner interfacial polarization. - Abstract: Polythiophene-tinoxide (PT-SnO{sub 2}) nanocomposites were prepared by in situ chemical oxidative polymerization, in the presence of various concentrations of SnO{sub 2} nanoparticles. Samples were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and Zeta potential measurements. Morphologies and elemental compositions were investigated by transmission electron microscopy, field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. The photoconductivity of the nanocomposites was studied by field-dependent dark and photo conductivity measurements. Their dielectric properties were investigated using dielectric spectroscopy, in the frequency range of 1kHz–1 MHz. The results indicated that the SnO{sub 2} nanoparticles in the PT-SnO{sub 2} nanocomposite were responsible for its enhanced dielectric performance.

Molecular dynamics simulations of the dielectric properties of fructose aqueous solutions

International Nuclear Information System (INIS)

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

2016-01-01

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

Enhanced transmission through arrays of subwavelength holes in gold films coated by a finite dielectric layer

DEFF Research Database (Denmark)

Xiao, Sanshui; Mortensen, Niels Asger; Qiu, M.

2007-01-01

resonances attributing to the enhanced transmission: the localized waveguide resonance and periodic surface plasmon resonances. For the film coated with dielectric layers, calculated results show that in the wavelength region of interest the localized waveguide resonant mode attributes to sensing rather than...

Contemporary dielectric materials

CERN Document Server

Saravanan, R

2016-01-01

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

Dielectric properties of Ga2O3-doped barium iron niobate ceramics

International Nuclear Information System (INIS)

Sanjoom, Kachaporn; Pengpat, Kamonpan; Eitssayeam, Sukum; Tunkasiri, Tawee; Rujijanagul, Gobwute

2014-01-01

Ga-doped BaFe 0.5 Nb 0.5 O 3 (Ba(Fe 1-x Ga x ) 0.5 Nb 0.5 O 3 ) ceramics were fabricated and their properties were investigated. All ceramics showed perovskite structure with cubic symmetry and the solubility of Ga in BFN ceramics had a limit at x = 0.2. Examination of the dielectric spectra indicated that all ceramic samples presented high dielectric constants that were frequency dependent. The x = 0.2 ceramic showed a very high dielectric constant (ε r > 240 000 at 1 kHz) while the x = 0.4 sample exhibited high thermal stability of dielectric constant with low loss tangent from room temperature (RT) to 100 C with ε r > 28 000 (at 1 kHz) when compared to other samples. By using a complex impedance analysis technique, bulk grain, grain boundary, and electrode response were found to affect the dielectric behavior that could be related to the Maxwell-Wagner polarization mechanism. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Gap deformation and classical wave localization in disordered two-dimensional photonic-band-gap materials

International Nuclear Information System (INIS)

Lidorikis, E.; Sigalas, M. M.; Economou, E. N.; Soukoulis, C. M.

2000-01-01

By using two ab initio numerical methods, we study the effects that disorder has on the spectral gaps and on wave localization in two-dimensional photonic-band-gap materials. We find that there are basically two different responses depending on the lattice realization (solid dielectric cylinders in air or vice versa), the wave polarization, and the particular form under which disorder is introduced. Two different pictures for the photonic states are employed, the ''nearly free'' photon and the ''strongly localized'' photon. These originate from the two different mechanisms responsible for the formation of the spectral gaps, i.e., multiple scattering and single scatterer resonances, and they qualitatively explain our results. (c) 2000 The American Physical Society

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

Czech Academy of Sciences Publication Activity Database

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

2006-01-01

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

Super Dielectric Materials

Directory of Open Access Journals (Sweden)

Samuel Fromille

2014-12-01

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

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

Science.gov (United States)

Alifakı, Yaşar Özlem; Şakıyan, Özge

2017-03-01

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

Manipulation of plasmonic resonances in graphene coated dielectric cylinders

KAUST Repository

Ge, Lixin

2016-11-16

Graphene sheets can support surface plasmon as the Dirac electrons oscillate collectively with electromagnetic waves. Compared with the surface plasmon in conventional metal (e.g., Ag and Au), graphene plasmonic owns many remarkable merits especially in Terahertz and far infrared frequencies, such as deep sub-wavelength, low loss, and high tunability. For graphene coated dielectric nano-scatters, localized surface plasmon (LSP)exist and can be excited under specific conditions. The LSPs are associated with the Mie resonance modes, leading to extraordinary large scattering and absorption cross section. In this work, we study systematically the optical scattering properties for graphene coated dielectric cylinders. It is found that the LSP can be manipulated by geometrical parameters and external electric gating. Generally, the resonance frequencies for different resonance modes are not the same. However, under proper design, we show that different resonance modes (e.g., dipole mode, quadruple mode etc.) can be excited at the same frequency. Thus, the scattering and absorption by graphene coated dielectric cylinders can indeed overcome the single channel limit. Our finding may open up new avenues in applications for the graphene-based THz optoelectronic devices.

Silicone-based Dielectric Elastomers

DEFF Research Database (Denmark)

Skov, Anne Ladegaard

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

Bistable scattering in graphene-coated dielectric nanowires.

Science.gov (United States)

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

2017-06-22

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

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

International Nuclear Information System (INIS)

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

1995-01-01

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

High temperature dielectric relaxation anomaly of Y3+ and Mn2+ doped barium strontium titanate ceramics

International Nuclear Information System (INIS)

Yan, Shiguang; Mao, Chaoliang; Wang, Genshui; Yao, Chunhua; Cao, Fei; Dong, Xianlin

2014-01-01

Relaxation like dielectric anomaly is observed in Y 3+ and Mn 2+ doped barium strontium titanate ceramics when the temperature is over 450 K. Apart from the conventional dielectric relaxation analysis method with Debye or modified Debye equations, which is hard to give exact temperature dependence of the relaxation process, dielectric response in the form of complex impedance, assisted with Cole-Cole impedance model corrected equivalent circuits, is adopted to solve this problem and chase the polarization mechanism in this paper. Through this method, an excellent description to temperature dependence of the dielectric relaxation anomaly and its dominated factors are achieved. Further analysis reveals that the exponential decay of the Cole distribution parameter n with temperature is confirmed to be induced by the microscopic lattice distortion due to ions doping and the interaction between the defects. At last, a clear sight to polarization mechanism containing both the intrinsic dipolar polarization and extrinsic distributed oxygen vacancies hopping response under different temperature is obtained.

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

International Nuclear Information System (INIS)

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

2015-01-01

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

Influence of Fe{sup 3+} substitution on the dielectric and ferroelectric characteristics of Lead Indium Niobate

Energy Technology Data Exchange (ETDEWEB)

Divya, A.S.; Kumar, V., E-mail: vkumar10@yahoo.com

2015-07-15

Highlights: • Prepared phase-pure Fe{sup 3+}-substituted Lead Indium Niobate, Pb[(In{sub 0.50−x}Fe{sub x})Nb{sub 0.50}]O{sub 3} by sol–gel method. • Spontaneous Relaxor (R) → Ferroelectric (FE) transition observed for the composition with x = 0.20. • Local structural rearrangement responsible for R → FE transition has been confirmed by Raman spectroscopy. - Abstract: Lead Indium Niobate, Pb(In{sub 0.50}Nb{sub 0.50})O{sub 3} (PIN) is a complex perovskite that exhibits Relaxor (R) characteristics. In this study, we report the synthesis of phase-pure compositions in the system Pb[(In{sub 0.50−x}Fe{sub x})Nb{sub 0.50}]O{sub 3} by sol–gel method and discuss the influence of isovalent substitution of Indium by Iron on the dielectric and ferroelectric characteristics. Spontaneous transition to the Ferroelectric (FE) phase has been observed for the composition having x = 0.20. Local structural rearrangements responsible for R → FE transition have also been studied by Raman spectroscopy and are discussed in detail.

Reversible dielectric property degradation in moisture-contaminated fiber-reinforced laminates

Science.gov (United States)

Rodriguez, Luis A.; García, Carla; Fittipaldi, Mauro; Grace, Landon R.

2016-03-01

The potential for recovery of dielectric properties of three water-contaminated fiber-reinforced laminates is investigated using a split-post dielectric resonant technique at X-band (10 GHz). The three material systems investigated are bismaleimide (BMI) reinforced with an eight-harness satin weave quartz fabric, an epoxy resin reinforced with an eight- harness satin weave glass fabric (style 7781), and the same epoxy reinforced with a four-harness woven glass fabric (style 4180). A direct correlation between moisture content, dielectric constant, and loss tangent was observed during moisture absorption by immersion in distilled water at 25 °C for five equivalent samples of each material system. This trend is observed through at least 0.72% water content by weight for all three systems. The absorption of water into the BMI, 7781 epoxy, and 4180 epoxy laminates resulted in a 4.66%, 3.35%, and 4.01% increase in dielectric constant for a 0.679%, 0.608%, and 0.719% increase in water content by weight, respectively. Likewise, a significant increase was noticed in loss tangent for each material. The same water content is responsible for a 228%, 71.4%, and 64.1% increase in loss tangent, respectively. Subsequent to full desorption through drying at elevated temperature, the dielectric constant and loss tangent of each laminate exhibited minimal change from the dry, pre-absorption state. The dielectric constant and loss tangent change after the absorption and desorption cycle, relative to the initial state, was 0.144 % and 2.63% in the BMI, 0.084% and 1.71% in the style 7781 epoxy, and 0.003% and 4.51% in the style 4180 epoxy at near-zero moisture content. The similarity of dielectric constant and loss tangent in samples prior to absorption and after desorption suggests that any chemical or morphological changes induced by the presence of water have not caused irreversible changes in the dielectric properties of the laminates.

Optics of dielectric microstructures

DEFF Research Database (Denmark)

Søndergaard, Thomas

2002-01-01

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

A generalized non-local optical response theory for plasmonic nanostructures

DEFF Research Database (Denmark)

Mortensen, N. Asger; Raza, Søren; Wubs, Martijn

2014-01-01

for their description. Here instead we present a comparatively simple semiclassical generalized non-local optical response theory that unifies quantum pressure convection effects and induced charge diffusion kinetics, with a concomitant complex-valued generalized non-local optical response parameter. Our theory...

Thermal dielectric function

International Nuclear Information System (INIS)

Moneta, M.

1999-01-01

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

Initial operations in local nuclear emergency response headquarter

International Nuclear Information System (INIS)

2012-06-01

As a result of the Fukushima nuclear accident due to the Great East Japan Earthquake and the tsunami that occurred thereafter, local nuclear emergency response headquarters (local headquarters) was set up at off-site center (OFC). However, several obstacles such as the collapse of means of communication resulting from severed communication lines, food and fuel shortage resulting from stagnant physical distribution, and increasing radiation dose around the center significantly restricted originally intended operation of local headquarters. In such severe situation, the personnel gathered at the OFC from the government, local public bodies and electric companies from March 11 to 15 acted without sufficient food, sleep or rest and did all they could against successively occurring unexpected challenges by using limited means of communication. However, issues requiring further consideration were activities of each functional group, location of OFC and the functions of equipment, machines and materials and reflecting the consideration results into future protective measures and revision of the manual for nuclear emergency response were greatly important. This report described investigated results on initial operations in local headquarters such as situation of activities conducted by local headquarters and operations at functional groups. (T. Tanaka)

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

Indian Academy of Sciences (India)

2017-06-24

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

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

International Nuclear Information System (INIS)

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

2005-01-01

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

Plasmonic nanostructures: local versus nonlocal response

DEFF Research Database (Denmark)

Toscano, Giuseppe; Wubs, Martijn; Xiao, Sanshui

2010-01-01

, and hence it is sensitive to possible narrow resonances that may arise due to strong electronic quantum confinement in the metal. This feature allows us to accurately determine which geometries are strongly affected by nonlocal response, for example regarding applications based on electric field enhancement......We study the importance of taking the nonlocal optical response of metals into account for accurate determination of optical properties of nanoplasmonic structures. Here we focus on the computational physics aspects of this problem, and in particular we report on the nonlocal-response package...... that we wrote for state-of the art numerical software, enabling us to take into account the nonlocal material response of metals for any arbitrarily shaped nanoplasmonic structures, without much numerical overhead as compared to the standard local response. Our method is a frequency-domain method...

Structure and performance of dielectric films based on self-assembled nanocrystals with a high dielectric constant.

Science.gov (United States)

Huang, Limin; Liu, Shuangyi; Van Tassell, Barry J; Liu, Xiaohua; Byro, Andrew; Zhang, Henan; Leland, Eli S; Akins, Daniel L; Steingart, Daniel A; Li, Jackie; O'Brien, Stephen

2013-10-18

Self-assembled films built from nanoparticles with a high dielectric constant are attractive as a foundation for new dielectric media with increased efficiency and range of operation, due to the ability to exploit nanofabrication techniques and emergent electrical properties originating from the nanoscale. However, because the building block is a discrete one-dimensional unit, it becomes a challenge to capture potential enhancements in dielectric performance in two or three dimensions, frequently due to surface effects or the presence of discontinuities. This is a recurring theme in nanoparticle film technology when applied to the realm of thin film semiconductor and device electronics. We present the use of chemically synthesized (Ba,Sr)TiO3 nanocrystals, and a novel deposition-polymerization technique, as a means to fabricate the dielectric layer. The effective dielectric constant of the film is tunable according to nanoparticle size, and effective film dielectric constants of up to 34 are enabled. Wide area and multilayer dielectrics of up to 8 cm(2) and 190 nF are reported, for which the building block is an 8 nm nanocrystal. We describe models for assessing dielectric performance, and distinct methods for improving the dielectric constant of a nanocrystal thin film. The approach relies on evaporatively driven assembly of perovskite nanocrystals with uniform size distributions in a tunable 7-30 nm size range, coupled with the use of low molecular weight monomer/polymer precursor chemistry that can infiltrate the porous nanocrystal thin film network post assembly. The intercrystal void space (low k dielectric volume fraction) is minimized, while simultaneously promoting intercrystal connectivity and maximizing volume fraction of the high k dielectric component. Furfuryl alcohol, which has good affinity to the surface of (Ba,Sr)TiO3 nanocrystals and miscibility with a range of solvents, is demonstrated to be ideal for the production of nanocomposites. The

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

International Nuclear Information System (INIS)

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

2010-01-01

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

Dielectric and electro-optical parameters of two ferroelectric liquid crystals: a comparative study

International Nuclear Information System (INIS)

Kumar Misra, Abhishek; Kumar Srivastava, Abhishek; Shukla, J P; Manohar, Rajiv

2008-01-01

Dielectric relaxation and an electro-optical study of two ferroelectric liquid crystals having different spontaneous polarizations (Felix 16/100 and Felix 17/000) showing SmC* and SmA phases have been performed in the temperature range 30-80 compfn C. The experimental data have been used to determine different relaxation parameters, viz. distribution parameter, relaxation frequency, dielectric strength and rotational viscosity. The Goldstone mode of dielectric permittivity has been well observed for both the samples under investigation. The activation energy of both the samples has also been determined by the best theoretical fitting of the Arrhenius plot. We have also evaluated the optical response time and anchoring energy coefficients from electro-optical measurement techniques for these samples.

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

Science.gov (United States)

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

2016-03-01

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

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

Indian Academy of Sciences (India)

WINTEC

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

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

Indian Academy of Sciences (India)

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

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

Indian Academy of Sciences (India)

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

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

Indian Academy of Sciences (India)

Sivabrata Sahu

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

Modeling the dielectric logging tool at high frequency

International Nuclear Information System (INIS)

Chew, W.C.

1987-01-01

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

Dielectric Modulated FET (DMFET)

Indian Academy of Sciences (India)

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

Dose response relationship in local radiotherapy for hepatocellular carcinoma

International Nuclear Information System (INIS)

Park, Hee Chul; Seong, Jin Sil; Han, Kwang Hyub; Chon, Chae Yoon; Moon, Young Myoung; Song, Jae Seok; Suh, Chang Ok

2001-01-01

In this study, it was investigated whether dose response relation existed or not in local radiotherapy for primary hepatocellular carcinoma. From January 1992 to March 2000, 158 patients were included in present study. Exclusion criteria included the presence of extrahepatic metastasis, liver cirrhosis of Child's class C, tumors occupying more than two thirds of the entire liver, and performance status on the ECOG scale of more than 3. Radiotherapy was given to the field including tumor with generous margin using 6, 10-MV X-ray. Mean tumor dose was 48.2±7.9 Gy in daily 1.8 Gy fractions. Tumor response was based on diagnostic radiologic examinations such as CT scan, MR imaging, hepatic artery angiography at 4-8 weeks following completion of treatment. Statistical analysis was done to investigate the existence of dose response relationship of local radiotherapy when it was applied to the treatment of primary hepatocellular carcinoma. An objective response was observed in 106 of 158 patients, giving a response rate of 67. 1%. Statistical analysis revealed that total dose was the most significant factor in relation to tumor response when local radiotherapy was applied to the treatment of primary hepatocellular carcinoma. Only 29.2% showed objective response in patients treated with dose less than 40 Gy, while 68.6% and 77.1 % showed major response in patients with 40-50 Gy and more than 50 Gy, respectively. Child-Pugh classification was significant factor in the development of ascites, overt radiation induced liver disease and gastroenteritis. Radiation dose was an important factor for development of radiation induced gastroduodenal ulcer. Present study showed the existence of dose response relationship in local radiotherapy for primary hepatocellular carcinoma. Only radiotherapy dose was a significant factor to predict the objective response. Further study is required to predict the maximal tolerance dose in consideration of liver function and non-irradiated liver

Dielectric properties of binary solutions a data handbook

CERN Document Server

Akhadov, Y Y

1980-01-01

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

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

Science.gov (United States)

Hann, Raiford E.

1991-01-01

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

Silver Nanowire/MnO2 Nanowire Hybrid Polymer Nanocomposites: Materials with High Dielectric Permittivity and Low Dielectric Loss.

Science.gov (United States)

Zeraati, Ali Shayesteh; Arjmand, Mohammad; Sundararaj, Uttandaraman

2017-04-26

This study reports the fabrication of hybrid nanocomposites based on silver nanowire/manganese dioxide nanowire/poly(methyl methacrylate) (AgNW/MnO 2 NW/PMMA), using a solution casting technique, with outstanding dielectric permittivity and low dielectric loss. AgNW was synthesized using the hard-template technique, and MnO 2 NW was synthesized employing a hydrothermal method. The prepared AgNW:MnO 2 NW (2.0:1.0 vol %) hybrid nanocomposite showed a high dielectric permittivity (64 at 8.2 GHz) and low dielectric loss (0.31 at 8.2 GHz), which are among the best reported values in the literature in the X-band frequency range (8.2-12.4 GHz). The superior dielectric properties of the hybrid nanocomposites were attributed to (i) dimensionality match between the nanofillers, which increased their synergy, (ii) better dispersion state of AgNW in the presence of MnO 2 NW, (iii) positioning of ferroelectric MnO 2 NW in between AgNWs, which increased the dielectric permittivity of nanodielectrics, thereby increasing dielectric permittivity of the hybrid nanocomposites, (iv) barrier role of MnO 2 NW, i.e., cutting off the contact spots of AgNWs and leading to lower dielectric loss, and (v) AgNW aligned structure, which increased the effective surface area of AgNWs, as nanoelectrodes. Comparison of the dielectric properties of the developed hybrid nanocomposites with the literature highlights their great potential for flexible capacitors.

Dielectric properties of lunar surface

Science.gov (United States)

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

2017-03-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-04-14

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

Numerical investigation of dielectric barrier discharges

Science.gov (United States)

Li, Jing

1997-12-01

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

Dielectric properties of Ga{sub 2}O{sub 3}-doped barium iron niobate ceramics

Energy Technology Data Exchange (ETDEWEB)

Sanjoom, Kachaporn [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Sri Ayutthaya Road, Bangkok, 10400 (Thailand); Pengpat, Kamonpan; Eitssayeam, Sukum; Tunkasiri, Tawee [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Rujijanagul, Gobwute [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Sri Ayutthaya Road, Bangkok, 10400 (Thailand)

2014-08-15

Ga-doped BaFe{sub 0.5}Nb{sub 0.5}O{sub 3} (Ba(Fe{sub 1-x}Ga{sub x}){sub 0.5}Nb{sub 0.5}O{sub 3}) ceramics were fabricated and their properties were investigated. All ceramics showed perovskite structure with cubic symmetry and the solubility of Ga in BFN ceramics had a limit at x = 0.2. Examination of the dielectric spectra indicated that all ceramic samples presented high dielectric constants that were frequency dependent. The x = 0.2 ceramic showed a very high dielectric constant (ε{sub r} > 240 000 at 1 kHz) while the x = 0.4 sample exhibited high thermal stability of dielectric constant with low loss tangent from room temperature (RT) to 100 C with ε{sub r} > 28 000 (at 1 kHz) when compared to other samples. By using a complex impedance analysis technique, bulk grain, grain boundary, and electrode response were found to affect the dielectric behavior that could be related to the Maxwell-Wagner polarization mechanism. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Ka Band Phase Locked Loop Oscillator Dielectric Resonator Oscillator for Satellite EHF Band Receiver

Directory of Open Access Journals (Sweden)

S. Coco

2008-01-01

Full Text Available This paper describes the design and fabrication of a Ka Band PLL DRO having a fundamental oscillation frequency of 19.250 GHz, used as local oscillator in the low-noise block of a down converter (LNB for an EHF band receiver. Apposite circuital models have been created to describe the behaviour of the dielectric resonator and of the active component used in the oscillator core. The DRO characterization and measurements have shown very good agreement with simulation results. A good phase noise performance is obtained by using a very high Q dielectric resonator.

Dielectric Spectroscopic Detection of Early Failures in 3-D Integrated Circuits.

Science.gov (United States)

Obeng, Yaw; Okoro, C A; Ahn, Jung-Joon; You, Lin; Kopanski, Joseph J

The commercial introduction of three dimensional integrated circuits (3D-ICs) has been hindered by reliability challenges, such as stress related failures, resistivity changes, and unexplained early failures. In this paper, we discuss a new RF-based metrology, based on dielectric spectroscopy, for detecting and characterizing electrically active defects in fully integrated 3D devices. These defects are traceable to the chemistry of the insolation dielectrics used in the through silicon via (TSV) construction. We show that these defects may be responsible for some of the unexplained early reliability failures observed in TSV enabled 3D devices.

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

International Nuclear Information System (INIS)

Xiao, Tiejun

2015-01-01

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

Cellulose Triacetate Dielectric Films For Capacitors

Science.gov (United States)

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

1994-01-01

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

Managing Corporate Responsibility Globally and Locally

DEFF Research Database (Denmark)

Brown, Dana; Knudsen, Jette Steen

2012-01-01

Corporate Responsibility (CR) is today an essential component of corporate global strategy. CR can bolster the institutional context for market expansion fill institutional voids or facilitate market entry as a component of non-market strategy. Yet, in fulfilling these functions, CR may need...... to be highly sensitive to local contexts. How can transnational firms organize CR so as to maximize efficiencies from globalization and to minimize the fragmentation of corporate organizational cultures? provide a framework for analyzing the way that corporations coordinate global and local functions. We build...... on this framework in a case study of Novo Nordisk and its approach to determining global and local CR policies and procedures with regard to its China and US subsidiaries. Our findings suggest that it is important for companies to define a common set of organizational norms. In addition, CR need to be sensitive...

Two optical bistability domains in composites of metal nanoparticles with nonlinear dielectric core

Energy Technology Data Exchange (ETDEWEB)

Shewamare, Sisay, E-mail: sisayshewa20@yahoo.com [Department of Physics, Addis Ababa University, P.O. Box 1176, Addis Ababa (Ethiopia); Mal' nev, V.N., E-mail: vadimnmalnev@yahoo.com [Department of Physics, Addis Ababa University, P.O. Box 1176, Addis Ababa (Ethiopia)

2012-12-15

It is shown that the local field in metal spherical particles with a dielectric core in an external varying electric field has two maxima at two different frequencies. The second maximum becomes more important with an increment in the metal fraction. Due to the nonlinear dielectric function of the core, the composite of these inclusions may have two optically induced bistability domains at different frequencies. At rather high metal fraction, two bistability domains merge and form one entire bistability domain. The parameters of these domains are studied numerically. The paper focuses on the second bistability domain, which has not been discussed in the literature so far. This domain exists in a comparatively narrow frequency range and its onset fields are lower than those of the first bistability domain. The lowest bistability onset fields are obtained in the entire domain. This peculiarity of the optical induced bistability in the metal composite with small dielectric cores can be attractive for possible applications.

Two optical bistability domains in composites of metal nanoparticles with nonlinear dielectric core

International Nuclear Information System (INIS)

Shewamare, Sisay; Mal'nev, V.N.

2012-01-01

It is shown that the local field in metal spherical particles with a dielectric core in an external varying electric field has two maxima at two different frequencies. The second maximum becomes more important with an increment in the metal fraction. Due to the nonlinear dielectric function of the core, the composite of these inclusions may have two optically induced bistability domains at different frequencies. At rather high metal fraction, two bistability domains merge and form one entire bistability domain. The parameters of these domains are studied numerically. The paper focuses on the second bistability domain, which has not been discussed in the literature so far. This domain exists in a comparatively narrow frequency range and its onset fields are lower than those of the first bistability domain. The lowest bistability onset fields are obtained in the entire domain. This peculiarity of the optical induced bistability in the metal composite with small dielectric cores can be attractive for possible applications.

An experimental study of electrical and dielectric properties of consolidated clayey materials

International Nuclear Information System (INIS)

Comparon, L.

2005-06-01

This study is devoted to the electrical and dielectric properties of consolidated clays. A better understanding of the conduction and polarization phenomena in clays is necessary to better interpret in situ measurements in terms of water saturation and texture. An experimental study was carried out on synthetic clay samples (kaolinite and smectite) compacted with various water contents, porosities and mineralogical compositions, on a large frequency range, using three laboratory setups. The electrical properties of natural argillites (from ANDRA) were then investigated. We found that the response of the synthetic samples is mainly controlled by water content on the whole frequency range; two polarization phenomena were observed, which were related to the Maxwell-Wagner polarization and the electrical double layer polarization around the clay particles. The electrical response of argillites is more complex; it is controlled by water content but also by the microstructure of the rock. In these rocks, the electrical and dielectric anisotropies are high; anisotropy was also measured for the synthetic clays. The existing models explain the high frequency limit of the dielectric permittivity of the clayey materials, but the low frequency part of the spectra (≤1 MHz) needs theoretical developments. (author)

Polarization-independent all-silicon dielectric metasurfaces in the terahertz regime

KAUST Repository

Zhang, Huifang

2017-12-11

Dielectric metasurfaces have achieved great success in realizing high-efficiency wavefront control in the optical and infrared ranges. Here, we experimentally demonstrate several efficient, polarization-independent, all-silicon dielectric metasurfaces in the terahertz regime. The metasurfaces are composed of cylindrical silicon pillars on a silicon substrate, which can be easily fabricated using etching technology for semiconductors. By locally tailoring the diameter of the pillars, full control over abrupt phase changes can be achieved. To show the controlling ability of the metasurfaces, an anomalous deflector, three Bessel beam generators, and three vortex beam generators are fabricated and characterized. We also show that the proposed metasurfaces can be easily combined to form composite devices with extended functionalities. The proposed controlling method has promising applications in developing low-loss, ultra-compact spatial terahertz modulation devices. (C) 2017 Chinese Laser Press

Polarization-independent all-silicon dielectric metasurfaces in the terahertz regime

KAUST Repository

Zhang, Huifang; Zhang, Xueqian; Xu, Quan; Wang, Qiu; Xu, Yuehong; Wei, Minggui; Li, Yanfeng; Gu, Jianqiang; Tian, Zhen; Ouyang, Chunmei; Zhang, Xixiang; Hu, Cong; Han, Jiaguang; Zhang, Weili

2017-01-01

Dielectric metasurfaces have achieved great success in realizing high-efficiency wavefront control in the optical and infrared ranges. Here, we experimentally demonstrate several efficient, polarization-independent, all-silicon dielectric metasurfaces in the terahertz regime. The metasurfaces are composed of cylindrical silicon pillars on a silicon substrate, which can be easily fabricated using etching technology for semiconductors. By locally tailoring the diameter of the pillars, full control over abrupt phase changes can be achieved. To show the controlling ability of the metasurfaces, an anomalous deflector, three Bessel beam generators, and three vortex beam generators are fabricated and characterized. We also show that the proposed metasurfaces can be easily combined to form composite devices with extended functionalities. The proposed controlling method has promising applications in developing low-loss, ultra-compact spatial terahertz modulation devices. (C) 2017 Chinese Laser Press

Dielectric relaxation in solid collagen over a wide temperature range

International Nuclear Information System (INIS)

Khan, Muhammad Abdullah; Rizvi, Tasneem Zahra; Janjua, Khalid Mehmood; Zaheer, Muhammad Yar

2001-07-01

Dielectric constant ε' and loss factor ε'' have been measured in bovine tendon collagen in the frequency range 30 Hz - 3 MHz and temperature range 30 deg. C to 200 deg. C. Frequency dependence curve of ε'' shows a low frequency strong α-dispersion attributed to phonon assisted proton hopping between localized sites and a weak high frequency. α 2 - dispersion attributed to reorientation of polar components of collagen molecules. Temperature dependence of the dielectric data show release of bound moisture as a three step process with discrete peaks at 50 deg. C, 90 deg. C and 125 deg. C. These peaks have been attributed to release of adsorbed surface water, water bound to exposed polar sites and strongly bound internal moisture respectively. A peak observed at 160 deg. C has been attributed to thermally induced helix-coil transition of collagen molecules. (author)

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

Indian Academy of Sciences (India)

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

'Non-local' response of RTP ohmic plasmas to peripheral perturbations

International Nuclear Information System (INIS)

Galli, P.; Gorini, G.; Mantica, P.; Hogeweij, G.M.D.; Kloe, J. de; Lopes Cardozo, N.J.

1999-01-01

A 'non-local' response of the plasma core triggered by peripheral plasma perturbations other than laser ablation is found in the RTP tokamak. Oblique pellet injection (OPI) has been used to induce fast cooling of the peripheral plasma. In response, an inward cold pulse (T e drop) and a slightly delayed core T e rise are observed. A somewhat similar 'non-local' response is observed when the peripheral plasma is heated by modulated electron cyclotron heating or by fast current ramps, i.e. the core temperature drops in response to the peripheral heating. The plasma conditions for the occurrence of the 'non-local' response have been investigated. The core T e rise following OPI is associated with the formation of a large temperature gradient in the region 1 e rise is largest at low electron density and for large pellet deposition radii. Above a critical density the T e rise disappears and only the (weaker) drop in core T e is observed. Time dependent transport simulations show that the propagation of the inward cold pulse is consistent with local transport, while the core T e rise is a slower phenomenon requiring a large transient drop of χ e in the region 1 < q < 2. (author)

Investigation of the dielectric properties of shale

International Nuclear Information System (INIS)

Martemyanov, Sergey M.

2011-01-01

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

Dielectric constant and electrical conductivity of contaminated fine-grained soils and barrier materials

International Nuclear Information System (INIS)

Kaya, A.; Fang, H.Y.; Inyang, H.I.

1997-01-01

Characterization of contaminated fine-grained soils and tracking of contaminant migration within barriers have been challenging because current methods and/or procedures are labor and time-intensive, and destructive. To demonstrate the effective use of both dielectric constant and electrical conductivity in the characterization of contaminated fine-grained soils, pore fluids were prepared at different ionic strengths, and were used as permeates for kaolinite, bentonite and a local soil. Then, both dielectric constant and electrical conductivity of the soils were measured by means of a capacitor over a wide range of frequencies and moisture content. It was observed that although each soil has its unique dielectric constant and electrical conductivity at a given moisture content, increases in ionic strength cause a decrease in the dielectric constant of the system at very high frequencies (MHZ), whereas the dielectric constant increases at low frequencies (kHz). Electrical conductivity of a soil-water system is independent of frequency. However, it is a function of ionic strength of the pore fluid. It is clearly demonstrated that dielectric constant and electrical conductivity of soils are functions of both moisture content and ionic strength, and can be used to characterize the spatial and temporal levels of contamination. This method/procedure can be used in estimating the level of contamination as well as the direction of contaminant movement in the subsurface without the use of extensive laboratory testing. Based on obtained results, it was concluded that the proposed method/procedure is promising because it is non-destructive and provides a quick means of assessing the spatial distribution of contaminants in fine-grained soils and barriers

Impact of structural changes on dielectric and thermal properties of vinylidene fluoride–trifluoroethylene-based terpolymer/copolymer blends

Energy Technology Data Exchange (ETDEWEB)

Casar, G. [Jožef Stefan Institute and Jožef Stefan International Postgraduate School, Jamova 39, SI-1000 Ljubljana (Slovenia); Li, X. [Department of Electrical Engineering and Materials Research Institute, The Pennsylvania State University, University Park, PA 16802 (United States); Malič, B. [Jožef Stefan Institute and Jožef Stefan International Postgraduate School, Jamova 39, SI-1000 Ljubljana (Slovenia); Zhang, Q.M. [Department of Electrical Engineering and Materials Research Institute, The Pennsylvania State University, University Park, PA 16802 (United States); Bobnar, V., E-mail: vid.bobnar@ijs.si [Jožef Stefan Institute and Jožef Stefan International Postgraduate School, Jamova 39, SI-1000 Ljubljana (Slovenia)

2015-03-15

We report dielectric and thermal properties of the poly(vinylidene fluoride–trifluoroethylene–chlorofluoroethylene) terpolymer [P(VDF–TrFE–CFE), a member of the relaxor polymer family that exhibits fast response speeds, giant electrostriction, high electric energy density, and large electrocaloric effect] blended with the ferroelectric poly(vinylidene fluoride–trifluoroethylene) copolymer, P(VDF–TrFE). Although the differential scanning calorimetry (DSC) clearly reveals that both components form separate crystalline phases, at low copolymer content blends entirely exhibit a relaxorlike linear dielectric response, since the interfacial couplings to the bulky defects in the terpolymer convert the normal ferroelectric copolymer into a relaxor. On the other hand, dielectric experiments evidence that in blends with 20–50 wt% of P(VDF–TrFE) the ferroelectric and relaxor states coexist. This coexistence is confirmed by DSC results, which further reveal the influence of blending on the terpolymer crystallinity and melting point. At last, the crystallinity data appropriately explain the variation of the dielectric constant in P(VDF–TrFE–CFE)/P(VDF–TrFE) blends.

Femtosecond self-reconfiguration of laser-induced plasma patterns in dielectrics

Science.gov (United States)

Déziel, Jean-Luc; Dubé, Louis J.; Messaddeq, Sandra H.; Messaddeq, Younès; Varin, Charles

2018-05-01

Laser-induced modification of transparent solids by intense femtosecond laser pulses allows fast integration of nanophotonic and nanofluidic devices with controlled optical properties. Experimental observations suggest that the local and dynamic nature of the interactions between light and the transient plasma plays an important role during fabrication. Current analytical models neglect these aspects and offer limited coverage of nanograting formation on dielectric surfaces. In this paper, we present a self-consistent dynamic treatment of the plasma buildup and its interaction with light within a three-dimensional electromagnetic framework. The main finding of this work is that local light-plasma interactions are responsible for the reorientation of laser-induced periodic plasma patterns with respect to the incident light polarization, when a certain energy density threshold is reached. Plasma reconfiguration occurs within a single laser pulse, on a femtosecond time scale. Moreover, we show that the reconfigured subwavelength plasma structures actually grow into the bulk of the sample, which agrees with the experimental observations of self-organized volume nanogratings. We find that mode coupling of the incident and transversely scattered light with the periodic plasma structures is sufficient to initiate the growth and self-organization of the pattern inside the medium with a characteristic half-wavelength periodicity.

Stress Transmission in Granular Packings: Localization and Cooperative Response

Science.gov (United States)

Ramola, Kabir

We develop a framework for stress transmission in two dimensional granular media that respects vector force balance at the microscopic level. For a packing of grains interacting via pairwise contact forces, we introduce local gauge degrees of freedom that determine the response of the system to external perturbations. This allows us to construct unique force-balanced solutions that determine the change in contact forces as a response to external stress. By mapping this response to diffusion in the underlying contact network, we show that this naturally leads to spatial localization of forces. We present numerical evidence for stress localization using exact diagonalization studies of network Laplacians associated with soft disk packings. We use this formalism to characterize the deviation from elastic behaviour as the amount of disorder in the underlying network is varied. We discuss generalizations to systems with large friction between grains and other networks that display topological disorder. This work has been supported by NSF-DMR 1409093 and the W. M. Keck Foundation.

Dielectric inspection of erythrocyte morphology

International Nuclear Information System (INIS)

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

2008-01-01

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

Dielectric inspection of erythrocyte morphology

Energy Technology Data Exchange (ETDEWEB)

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

2008-05-21

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

Laser amplification in excited dielectrics

DEFF Research Database (Denmark)

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

2018-01-01

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

Electrical breakdown phenomena of dielectric elastomers

DEFF Research Database (Denmark)

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

2017-01-01

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

Single-layer graphene-assembled 3D porous carbon composites with PVA and Fe₃O₄ nano-fillers: an interface-mediated superior dielectric and EMI shielding performance.

Science.gov (United States)

Rao, B V Bhaskara; Yadav, Prasad; Aepuru, Radhamanohar; Panda, H S; Ogale, Satishchandra; Kale, S N

2015-07-28

In this study, a novel composite of Fe3O4 nanofiller-decorated single-layer graphene-assembled porous carbon (SLGAPC) with polyvinyl alcohol (PVA) having flexibility and a density of 0.75 g cm(-3) is explored for its dielectric and electromagnetic interference (EMI) response properties. The composite is prepared by the solution casting method and its constituents are optimized as 15 wt% SLGAPC and 20 wt% Fe3O4 through a novel solvent relaxation nuclear magnetic resonance experiment. The PVA-SLGAPC-Fe3O4 composite shows high dielectric permittivity in the range of 1 Hz-10 MHz, enhanced by a factor of 4 as compared to that of the PVA-SLGAPC composite, with a reduced loss by a factor of 2. The temperature dependent dielectric properties reveal the activation energy behaviour with reference to the glass transition temperature (80 °C) of PVA. The dielectric hysteresis with the temperature cycle reveals a remnant polarization. The enhanced dielectric properties are suggested to be the result of improvement in the localized polarization of the integrated interface system (Maxwell-Wagner-Sillars (MWS) polarization) formed by the uniform adsorption of Fe3O4 on the surface of SLGAPC conjugated with PVA. The EMI shielding property of the composite with a low thickness of 0.3 mm in the X-band (8.2-12.4 GHz) shows a very impressive shielding efficiency of ∼15 dB and a specific shielding effectiveness of 20 dB (g cm(-3))(-1), indicating the promising character of this material for flexible EMI shielding applications.

Electromagnetic Properties of Multiphase Dielectrics A Primer on Modeling, Theory and Computation

CERN Document Server

Zohdi, Tarek I

2012-01-01

Recently, several applications, primarily driven by microtechnology, have emerged where the use of materials with  tailored  electromagnetic  (dielectric) properties are necessary for a successful  overall design.  The ``tailored'' aggregate properties are achieved by combining an easily moldable  base matrix with particles  having dielectric properties that are chosen to deliver (desired) effective properties. In many cases, the analysis of such materials requires the simulation of the macroscopic and microscopic electromagnetic response, as well as its resulting coupled thermal response,  which can be important to determine possible failures in ``hot spots.'' This necessitates   a stress analysis. Furthermore, because, oftentimes, such processes initiate degratory chemical processes, it can be necessary to also include models for these processes as well.   A central  objective of this work is to provide basic models and numerical solution strategies to analyze the coupled response of such mat...

Light Scattering by a Dielectric Sphere: Perspectives on the Mie Resonances

Directory of Open Access Journals (Sweden)

Dimitrios Tzarouchis

2018-01-01

Full Text Available Light scattering by a small spherical particle, a central topic for electromagnetic scattering theory, is here considered. In this short review, some of the basic features of its resonant scattering behavior are covered. First, a general physical picture is described by a full electrodynamic perspective, the Lorenz–Mie theory. The resonant spectrum of a dielectric sphere reveals the existence of two distinctive types of polarization enhancement: the plasmonic and the dielectric resonances. The corresponding electrostatic (Rayleigh picture is analyzed and the polarizability of a homogeneous spherical inclusion is extracted. This description facilitates the identification of the first type of resonance, i.e., the localized surface plasmon (plasmonic resonance, as a function of the permittivity. Moreover, the electrostatic picture is linked with the plasmon hybridization model through the case of a step-inhomogeneous structure, i.e., a core–shell sphere. The connections between the electrostatic and electrodynamic models are reviewed in the small size limit and details on size-induced aspects, such as the dynamic depolarization and the radiation reaction on a small sphere are exposed through the newly introduced Mie–Padé approximative perspective. The applicability of this approximation is further expanded including the second type of resonances, i.e., the dielectric resonances. For this type of resonances, the Mie–Padé approximation reveals the main character of the two different cases of resonances of either magnetic or electric origin. A unified picture is therefore described encompassing both plasmonic and dielectric resonances, and the resonant conditions of all three different types are extracted as functions of the permittivity and the size of the sphere. Lastly, the directional scattering behavior of the first two dielectric resonances is exposed in a simple manner, namely the Kerker conditions for maximum forward and

Applicability of point-dipoles approximation to all-dielectric metamaterials

DEFF Research Database (Denmark)

Kuznetsova, S. M.; Andryieuski, Andrei; Lavrinenko, Andrei

2015-01-01

All-dielectric metamaterials consisting of high-dielectric inclusions in a low-dielectric matrix are considered as a low-loss alternative to resonant metal-based metamaterials. In this paper we investigate the applicability of the point electric and magnetic dipoles approximation to dielectric meta......-atoms on the example of a dielectric ring metamaterial. Despite the large electrical size of high-dielectric meta-atoms, the dipole approximation allows for accurate prediction of the metamaterials properties for the rings with diameters up to approximate to 0.8 of the lattice constant. The results provide important...... guidelines for design and optimization of all-dielectric metamaterials....

The color dielectric model of QCD

International Nuclear Information System (INIS)

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

1992-01-01

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

Analysis of electron interactions in dielectric gases

International Nuclear Information System (INIS)

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

2007-01-01

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

Plasmon transmutation: inducing new modes in nanoclusters by adding dielectric nanoparticles.

Science.gov (United States)

Wen, Fangfang; Ye, Jian; Liu, Na; Van Dorpe, Pol; Nordlander, Peter; Halas, Naomi J

2012-09-12

Planar clusters of coupled plasmonic nanoparticles support nanoscale electromagnetic "hot spots" and coherent effects, such as Fano resonances, with unique near and far field signatures, currently of prime interest for sensing applications. Here we show that plasmonic cluster properties can be substantially modified by the addition of individual, discrete dielectric nanoparticles at specific locations on the cluster, introducing new plasmon modes, or transmuting existing plasmon modes to new ones, in the resulting metallodielectric nanocomplex. Depositing a single carbon nanoparticle in the junction between a pair of adjacent nanodisks induces a metal-dielectric-metal quadrupolar plasmon mode. In a ten-membered cluster, placement of several carbon nanoparticles in junctions between multiple adjacent nanoparticles introduces a collective magnetic plasmon mode into the Fano dip, giving rise to an additional subradiant mode in the metallodielectric nanocluster response. These examples illustrate that adding dielectric nanoparticles to metallic nanoclusters expands the number and types of plasmon modes supported by these new mixed-media nanoscale assemblies.

Toward the Physical Basis of Complex Systems: Dielectric Analysis of Porous Silicon Nanochannels in the Electrical Double Layer Length Range

Directory of Open Access Journals (Sweden)

Radu Mircea Ciuceanu

2011-01-01

Full Text Available Dielectric analysis (DEA shows changes in the properties of
a materials as a response to the application on it of a time dependent electric field. Dielectric measurements are extremely sensitive to small changes in materials properties, that molecular relaxation, dipole changes, local motions that involve the reorientation of dipoles, and so can be observed by DEA. Electrical double layer (EDL, consists in a shielding layer that is naturally created within the liquid near a charged surface. The thickness of the EDL is given by the characteristic Debye length what grows less with the ionic strength defined by half summ products of concentration with square of charge for all solvent
ions (co-ions, counterions, charged molecules. The typical length scale for the Debye length is on the order of 1 nm, depending on the ionic contents in the solvent; thus, the EDL becomes significant for nano-capillaries that nanochannels. The electrokinetic e®ects in the nanochannels depend essentialy on the distribution of charged species in EDL, described by the Poisson-Boltzmann equation those solutions require the solvent dielectric permittivity. In this work we propose a model for solvent low-frequency permittivity and a DEA profile taking into account both the porous silicon electrode and aqueous solvent properties in the Debye length range.

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

International Nuclear Information System (INIS)

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

2009-01-01

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

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

Science.gov (United States)

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

2009-07-01

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

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

Science.gov (United States)

Sikdar, Debabrata; Kornyshev, Alexei A

2016-09-22

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

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

Czech Academy of Sciences Publication Activity Database

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

2010-01-01

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

Advanced dielectric continuum model of preferential solvation

Science.gov (United States)

Basilevsky, Mikhail; Odinokov, Alexey; Nikitina, Ekaterina; Grigoriev, Fedor; Petrov, Nikolai; Alfimov, Mikhail

2009-01-01

A continuum model for solvation effects in binary solvent mixtures is formulated in terms of the density functional theory. The presence of two variables, namely, the dimensionless solvent composition y and the dimensionless total solvent density z, is an essential feature of binary systems. Their coupling, hidden in the structure of the local dielectric permittivity function, is postulated at the phenomenological level. Local equilibrium conditions are derived by a variation in the free energy functional expressed in terms of the composition and density variables. They appear as a pair of coupled equations defining y and z as spatial distributions. We consider the simplest spherically symmetric case of the Born-type ion immersed in the benzene/dimethylsulfoxide (DMSO) solvent mixture. The profiles of y(R ) and z(R ) along the radius R, which measures the distance from the ion center, are found in molecular dynamics (MD) simulations. It is shown that for a given solute ion z(R ) does not depend significantly on the composition variable y. A simplified solution is then obtained by inserting z(R ), found in the MD simulation for the pure DMSO, in the single equation which defines y(R ). In this way composition dependences of the main solvation effects are investigated. The local density augmentation appears as a peak of z(R ) at the ion boundary. It is responsible for the fine solvation effects missing when the ordinary solvation theories, in which z =1, are applied. These phenomena, studied for negative ions, reproduce consistently the simulation results. For positive ions the simulation shows that z ≫1 (z =5-6 at the maximum of the z peak), which means that an extremely dense solvation shell is formed. In such a situation the continuum description fails to be valid within a consistent parametrization.

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

International Nuclear Information System (INIS)

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

2014-01-01

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

Charge accumulation in lossy dielectrics: a review

DEFF Research Database (Denmark)

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

1999-01-01

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

Depolarization current relaxation process of insulating dielectrics after corona poling under different charging conditions

Directory of Open Access Journals (Sweden)

J. W. Zhang

2017-10-01

Full Text Available As an insulating dielectric, polyimide is favorable for the application of optoelectronics, electrical insulation system in electric power industry, insulating, and packaging materials in space aircraft, due to its excellent thermal, mechanical and electrical insulating stability. The charge storage profile of such insulating dielectric is utmost important to its application, when it is exposed to electron irradiation, high voltage corona discharge or other treatments. These treatments could induce changes in physical and chemical properties of treated samples. To investigate the charge storage mechanism of the insulating dielectrics after high-voltage corona discharge, the relaxation processes responsible for corona charged polyimide films under different poling conditions were analyzed by the Thermally Stimulated Discharge Currents method (TSDC. In the results of thermal relaxation process, the appearance of various peaks in TSDC spectra provided a deep insight into the molecular status in the dielectric material and reflected stored space charge relaxation process in the insulating polymers after corona discharge treatments. Furthermore, the different space charge distribution status under various poling temperature and different discharge voltage level were also investigated, which could partly reflect the influence of the ambiance condition on the functional dielectrics after corona poling.

Depolarization current relaxation process of insulating dielectrics after corona poling under different charging conditions

Science.gov (United States)

Zhang, J. W.; Zhou, T. C.; Wang, J. X.; Yang, X. F.; Zhu, F.; Tian, L. M.; Liu, R. T.

2017-10-01

As an insulating dielectric, polyimide is favorable for the application of optoelectronics, electrical insulation system in electric power industry, insulating, and packaging materials in space aircraft, due to its excellent thermal, mechanical and electrical insulating stability. The charge storage profile of such insulating dielectric is utmost important to its application, when it is exposed to electron irradiation, high voltage corona discharge or other treatments. These treatments could induce changes in physical and chemical properties of treated samples. To investigate the charge storage mechanism of the insulating dielectrics after high-voltage corona discharge, the relaxation processes responsible for corona charged polyimide films under different poling conditions were analyzed by the Thermally Stimulated Discharge Currents method (TSDC). In the results of thermal relaxation process, the appearance of various peaks in TSDC spectra provided a deep insight into the molecular status in the dielectric material and reflected stored space charge relaxation process in the insulating polymers after corona discharge treatments. Furthermore, the different space charge distribution status under various poling temperature and different discharge voltage level were also investigated, which could partly reflect the influence of the ambiance condition on the functional dielectrics after corona poling.

Dielectric response and room temperature ferromagnetism in Cr doped anatase TiO2 nanoparticles

Science.gov (United States)

Naseem, Swaleha; Khan, Wasi; Khan, Shakeel; Husain, Shahid; Ahmad, Abid

2018-02-01

In the present work, nanocrystalline samples of Ti1-xCrxO2 (x = 0, 0.02, 0.04, 0.06 and 0.08) were synthesized in anatase phase through simple and cost effective acid modified sol gel method. The influence of Cr doping on thermal, microstructural, electrical and magnetic properties was investigated in TiO2 host matrix. The surface morphology has revealed less agglomeration and considerable reduction in particle size in case of Cr doped TiO2 as compared to undoped TiO2 nanoparticles (NPs). Energy dispersive x-ray spectroscopy (EDS), Raman and X-ray photoelectron spectroscopy (XPS) established high purity, appropriate stoichiometry and oxidation states of the compositions. The dielectric properties of the nanoparticles were altered by the doping concentration, applied frequency as well as temperature variation. The variation in dielectric constant (ε‧), dielectric loss (δ) and ac conductivity as a function of frequency and temperature at different doping concentration of Cr were interpreted in the light of Maxwell Wagner theory, space charge polarization mechanism and drift mobility of charge carriers. Both undoped and Cr doped TiO2 samples exhibit room temperature ferromagnetism (RTFM) that remarkably influenced by means of the Cr content. The significant enhancement in the magnetization was observed at 4% Cr doping. However, decrease in magnetization for higher doping signify antiferromagnetic interactions between Cr ions or superexchange mechanism. These results reveal that the oxygen vacancies play a crucial role to initiate the RTFM. Therefore, the present investigation suggests the potential applications of Cr doped TiO2 nanoparticles for spintronics application.

Dielectric Actuation of Polymers

Science.gov (United States)

Niu, Xiaofan

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

Atomistic determination of flexoelectric properties of crystalline dielectrics

Science.gov (United States)

Maranganti, R.; Sharma, P.

2009-08-01

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

Dielectric Properties of Flocculated Water-in-Oil Emulsions

Energy Technology Data Exchange (ETDEWEB)

Skodvin, T.

1995-12-31

When an offshore oil field is near completion, water occupies a large fraction of the available pore volume. Thus, in collecting the oil and gas reserves, one has to deal with a high co-production of either formation- or injected water. This doctoral thesis focuses on the effect of water-in-oil emulsions on the dielectric properties, in particular the effect of flocculation. Various dielectric models are applied to obtain methods for qualitative and quantitative characterization of the flocculated state. Permittivity and measurement of dielectric properties are discussed as a basis for the interpretation of the dielectric properties of the emulsions. Various flocculation models are presented. It is concluded that the dielectric properties of water-in-oil emulsions are strongly influenced by continuously ongoing processes in the system. Because of flocculation and sedimentation the traditional dielectric mixture models cannot satisfactorily predict the dielectric behaviour. The experimentally obtained permittivities for the emulsions can be reproduced by including flocculation in the models and treating the floc aggregates as spheroids or subsystems with dielectric properties given by the degree of flocculation. The models discussed have difficulties reproducing the complete frequency behaviour found experimentally. This is probably because the dielectric relaxation may be influenced by processes not included in the models, such as the effects of dipolar or multipolar interactions between the droplets. For further research it is recommended that rheological and dielectric measurements be combined. 227 refs., 61 figs., 16 tabs.

Dielectric Properties of Flocculated Water-in-Oil Emulsions

Energy Technology Data Exchange (ETDEWEB)

Skodvin, T

1996-12-31

When an offshore oil field is near completion, water occupies a large fraction of the available pore volume. Thus, in collecting the oil and gas reserves, one has to deal with a high co-production of either formation- or injected water. This doctoral thesis focuses on the effect of water-in-oil emulsions on the dielectric properties, in particular the effect of flocculation. Various dielectric models are applied to obtain methods for qualitative and quantitative characterization of the flocculated state. Permittivity and measurement of dielectric properties are discussed as a basis for the interpretation of the dielectric properties of the emulsions. Various flocculation models are presented. It is concluded that the dielectric properties of water-in-oil emulsions are strongly influenced by continuously ongoing processes in the system. Because of flocculation and sedimentation the traditional dielectric mixture models cannot satisfactorily predict the dielectric behaviour. The experimentally obtained permittivities for the emulsions can be reproduced by including flocculation in the models and treating the floc aggregates as spheroids or subsystems with dielectric properties given by the degree of flocculation. The models discussed have difficulties reproducing the complete frequency behaviour found experimentally. This is probably because the dielectric relaxation may be influenced by processes not included in the models, such as the effects of dipolar or multipolar interactions between the droplets. For further research it is recommended that rheological and dielectric measurements be combined. 227 refs., 61 figs., 16 tabs.

High thermal conductivity lossy dielectric using a multi layer configuration

Science.gov (United States)

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

2003-01-01

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

Electrical actuation of dielectric droplets

International Nuclear Information System (INIS)

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

2008-01-01

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

Trends of microwave dielectric materials for antenna application

International Nuclear Information System (INIS)

Sulong, T. A. T.; Osman, R. A. M.; Idris, M. S.

2016-01-01

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

Dielectric spectroscopy of watermelons for quality sensing

Science.gov (United States)

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

2007-07-01

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

Properties of dielectric barrier discharges in different arrangements

International Nuclear Information System (INIS)

Pietsch, G.J.

2001-01-01

Dielectric barrier discharges (DBDs) occur in arrangements where at least one dielectric is positioned in a gas space in between conducting electrodes. When breakdown field strength is reached in such a device, charge carriers are created in the gas region, accelerated, multiplied and finally collected on the surface(s) of the dielectric(s). The charge accumulation on the dielectric creates a counter field to that resulting from the power supply and as all of these processes are rather fast, the discharge quenches rapidly. The dielectric has two tasks, it limits the transferred charge and by this the energy conversion and distributes the discharge over the electrode area. That is why DBDs are non-thermal discharges which exist even at atmospheric pressure

Theoretical Modeling and Analysis of L- and P-band Radar Backscatter Sensitivity to Soil Active Layer Dielectric Variations

Directory of Open Access Journals (Sweden)

Jinyang Du

2015-07-01

Full Text Available Freeze-thaw (FT and moisture dynamics within the soil active layer are critical elements of boreal, arctic and alpine ecosystems, and environmental change assessments. We evaluated the potential for detecting dielectric changes within different soil layers using combined L- and P-band radar remote sensing as a prerequisite for detecting FT and moisture profile changes within the soil active layer. A two-layer scattering model was developed and validated for simulating radar responses from vertically inhomogeneous soil. The model simulations indicated that inhomogeneity in the soil dielectric profile contributes to both L- and P-band backscatter, but with greater P-band sensitivity at depth. The difference in L- and P-band responses to soil dielectric profile inhomogeneity appears suitable for detecting associated changes in soil active layer conditions. Additional evaluation using collocated airborne radar (AIRSAR observations and in situ soil moisture measurements over alpine tundra indicates that combined L- and P-band SAR observations are sensitive to soil dielectric profile heterogeneity associated with variations in soil moisture and FT conditions.

Joint Testlet Cognitive Diagnosis Modeling for Paired Local Item Dependence in Response Times and Response Accuracy

Directory of Open Access Journals (Sweden)

Peida Zhan

2018-04-01

Full Text Available In joint models for item response times (RTs and response accuracy (RA, local item dependence is composed of local RA dependence and local RT dependence. The two components are usually caused by the same common stimulus and emerge as pairs. Thus, the violation of local item independence in the joint models is called paired local item dependence. To address the issue of paired local item dependence while applying the joint cognitive diagnosis models (CDMs, this study proposed a joint testlet cognitive diagnosis modeling approach. The proposed approach is an extension of Zhan et al. (2017 and it incorporates two types of random testlet effect parameters (one for RA and the other for RTs to account for paired local item dependence. The model parameters were estimated using the full Bayesian Markov chain Monte Carlo (MCMC method. The 2015 PISA computer-based mathematics data were analyzed to demonstrate the application of the proposed model. Further, a brief simulation study was conducted to demonstrate the acceptable parameter recovery and the consequence of ignoring paired local item dependence.

The Dielectric Constant of Lubrication Oils

National Research Council Canada - National Science Library

Carey, A

1998-01-01

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

Quantifying Local, Response Dependence between Two Polytomous Items Using the Rasch Model

Science.gov (United States)

Andrich, David; Humphry, Stephen M.; Marais, Ida

2012-01-01

Models of modern test theory imply statistical independence among responses, generally referred to as "local independence." One violation of local independence occurs when the response to one item governs the response to a subsequent item. Expanding on a formulation of this kind of violation as a process in the dichotomous Rasch model,…

Method for fabrication of crack-free ceramic dielectric films

Energy Technology Data Exchange (ETDEWEB)

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

2017-12-05

The invention provides a process for forming crack-free dielectric films on a substrate. The process comprises the application of a dielectric precursor layer of a thickness from about 0.3 .mu.m to about 1.0 .mu.m to a substrate. The deposition is followed by low temperature heat pretreatment, prepyrolysis, pyrolysis and crystallization step for each layer. The deposition, heat pretreatment, prepyrolysis, pyrolysis and crystallization are repeated until the dielectric film forms an overall thickness of from about 1.5 .mu.m to about 20.0 .mu.m and providing a final crystallization treatment to form a thick dielectric film. The process provides a thick crack-free dielectric film on a substrate, the dielectric forming a dense thick crack-free dielectric having an overall dielectric thickness of from about 1.5 .mu.m to about 20.0 .mu.m.

Method for fabrication of crack-free ceramic dielectric films

Science.gov (United States)

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

2014-02-11

The invention provides a process for forming crack-free dielectric films on a substrate. The process comprise the application of a dielectric precursor layer of a thickness from about 0.3 .mu.m to about 1.0 .mu.m to a substrate. The deposition is followed by low temperature heat pretreatment, prepyrolysis, pyrolysis and crystallization step for each layer. The deposition, heat pretreatment, prepyrolysis, pyrolysis and crystallization are repeated until the dielectric film forms an overall thickness of from about 1.5 .mu.m to about 20.0 .mu.m and providing a final crystallization treatment to form a thick dielectric film. Also provided was a thick crack-free dielectric film on a substrate, the dielectric forming a dense thick crack-free dielectric having an overall dielectric thickness of from about 1.5 .mu.m to about 20.0 .mu.m.

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

Directory of Open Access Journals (Sweden)

M. Maria Sylvester

2017-08-01

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

Optimization of silver-dielectric-silver nanoshell for sensing applications

International Nuclear Information System (INIS)

Shirzaditabar, Farzad; Saliminasab, Maryam

2013-01-01

In this paper, resonance light scattering (RLS) properties of a silver-dielectric-silver nanoshell, based on quasi-static approach and plasmon hybridization theory, are investigated. Scattering spectrum of silver-dielectric-silver nanoshell has two intense and clearly separated RLS peaks and provides a potential for biosensing based on surface plasmon resonance and surface-enhanced Raman scattering. The two RLS peaks in silver-dielectric-silver nanoshell are optimized by tuning the geometrical dimensions. In addition, the optimal geometry is discussed to obtain the high sensitivity of silver-dielectric-silver nanoshell. As the silver core radius increases, the sensitivity of silver-dielectric-silver nanoshell decreases whereas increasing the middle dielectric thickness increases the sensitivity of silver-dielectric-silver nanoshell

Polaron-electron assisted giant dielectric dispersion in SrZrO{sub 3} high-k dielectric

Energy Technology Data Exchange (ETDEWEB)

Borkar, Hitesh; Barvat, Arun; Pal, Prabir; Kumar, Ashok, E-mail: ashok553@nplindia.org [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-National Physical Laboratory (CSIR-NPL) Campus, Dr. K S Krishnan Marg, New Delhi 110012 (India); Shukla, A. K. [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Pulikkotil, J. J. [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-National Physical Laboratory (CSIR-NPL) Campus, Dr. K S Krishnan Marg, New Delhi 110012 (India); Computation and Networking Facility, CSIR-National Physical Laboratory, New Delhi 110012 (India)

2016-06-07

The SrZrO{sub 3} is a well known high-k dielectric constant (∼22) and high optical bandgap (∼5.8 eV) material and one of the potential candidates for future generation nanoelectronic logic elements (8 nm node technology) beyond silicon. Its dielectric behavior is fairly robust and frequency independent till 470 K; however, it suffers a strong small-polaron based electronic phase transition (T{sub e}) linking 650 to 750 K. The impedance spectroscopy measurements revealed the presence of conducting grains and grain boundaries at elevated temperature which provide energetic mobile charge carriers with activation energy in the range of 0.7 to 1.2 eV supporting the oxygen ions and proton conduction. X-ray photoemission spectroscopy measurements suggest the presence of weak non-stoichiometric O{sup 2−} anions and hydroxyl species bound to different sites at the surface and bulk. These thermally activated charge carriers at elevated temperature significantly contribute to the polaronic based dielectric anomaly and conductivity. Our dielectric anomaly supports pseudo phase transition due to high degree of change in ZrO{sub 6} octahedral angle in the temperature range of 650–750 K, where electron density and phonon vibration affect the dielectric and conductivity properties.

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

International Nuclear Information System (INIS)

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

2006-01-01

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

Trends of microwave dielectric materials for antenna application

Energy Technology Data Exchange (ETDEWEB)

Sulong, T. A. T., E-mail: tuanamirahtuansulong@gmail.com; Osman, R. A. M., E-mail: rozana@unimap.edu.my [School of Microelectronic Engineering, Universiti Malaysia Perlis, Pauh Putra Campus, 02600 Arau, Perlis (Malaysia); Idris, M. S., E-mail: sobri@unimap.edu.my [Sustainable Engineering Research Cluster, School of Material Engineering, Universiti Malaysia Perlis, Blok B, Taman Pertiwi Indah, Seriab, 01000 Kangar, Perlis (Malaysia)

2016-07-19

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

Refractive index dependent local electric field enhancement in cylindrical gold nanohole

International Nuclear Information System (INIS)

Zhu Jian

2011-01-01

We report on the local electric field characters in a long cylindrical gold nanohole. Theoretical calculation results based on quasi-static model show that the local environmental dielectric constant dependent electric field intensity and field distribution in the gold nanohole show quite unique properties, different from those in the thin gold nanotube. Because of the thick gold wall, no plasmon hybridization exists. So there is only one resonance frequency taking place, and the intense local field has been focused into the gold nanohole. Our main finding is that, the local field in the nanohole is largely dependent on the inner hole refractive index and outer environmental refractive index. The competition between inner hole and outer polarization leads to a non-monotonic change of the local field intensity with increasing the dielectric constant of the nanohole. This refractive index controlled local field enhancement in cylindrical gold nanohole presents a potential for tunable surface-enhanced fluorescence and novel nano-optical biosensing applications.

Electronic transport and dielectric properties of low-dimensional structures of layered transition metal dichalcogenides

Energy Technology Data Exchange (ETDEWEB)

Kumar, Ashok, E-mail: ashok.1777@yahoo.com; Ahluwalia, P.K., E-mail: pk_ahluwalia7@yahoo.com

2014-02-25

Graphical abstract: We present electronic transport and dielectric response of layered transition metal dichalcogenides nanowires and nanoribbons. Illustration 1: Conductance (G) and corresponding local density of states(LDOS) for LTMDs wires at applied bias. I–V characterstics are shown in lowermost panels. Highlights: • The studied configurations show metallic/semiconducting nature. • States around the Fermi energy are mainly contributed by the d orbitals of metal atoms. • The studied configurations show non-linear current–voltage (I–V) characteristics. • Additional plasmonic features at low energy have been observed for both wires and ribbons. • Dielectric functions for both wires and ribbons are anisotropic (isotropic) at low (high) energy range. -- Abstract: We present first principle study of the electronic transport and dielectric properties of nanowires and nanoribbons of layered transition metal dichalcogenides (LTMDs), MX{sub 2} (M = Mo, W; X = S, Se, Te). The studied configuration shows metallic/semiconducting nature and the states around the Fermi energy are mainly contributed by the d orbitals of metal atoms. Zero-bias transmission show 1G{sub 0} conductance for the ribbons of MoS{sub 2} and WS{sub 2}; 2G{sub 0} conductance for MoS{sub 2}, WS{sub 2}, WSe{sub 2} wires, and ribbons of MoTe{sub 2} and WTe{sub 2}; and 3G{sub 0} conductance for WSe{sub 2} ribbon. The studied configurations show non-linear current–voltage (I–V) characteristics. Negative differential conductance (NDC) has also been observed for the nanoribbons of the selenides and tellurides of both Mo and W. Furthermore, additional plasmonic features below 5 eV energy have been observed for both wires and ribbons as compared to the corresponding monolayers, which is found to be red-shifted on going from nanowires to nanoribbons.

Dielectric properties of agricultural materials and their applications

CERN Document Server

Nelson, Stuart

2015-01-01

Dielectric Properties of Agricultural Materials and Their Applications provides an understanding of the fundamental principles governing dielectric properties of materials, describes methods for measuring such properties, and discusses many applications explored for solving industry problems. The information in this reference stimulates new research for solving problems associated with production, handling, and processing of agricultural and food products. Anyone seeking a better understanding of dielectric properties of materials and application of radio-frequency and microwave electromagnetic energy for solution of problems in agriculture and related fields will find this an essential resource. Presents applications of dielectric properties for sensing moisture in grain and seed and the use of such properties in radio-frequency and microwave dielectric heating of agricultural materials Offers information for finding correlations between dielectric properties and quality attributes such as sweetness in melon...

Evaluation of high temperature capacitor dielectrics

Science.gov (United States)

Hammoud, Ahmad N.; Myers, Ira T.

1992-01-01

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

Nonlocality and particle-clustering effects on the optical response of composite materials with metallic nanoparticles

Science.gov (United States)

Chen, C. W.; Chung, H. Y.; Chiang, H.-P.; Lu, J. Y.; Chang, R.; Tsai, D. P.; Leung, P. T.

2010-10-01

The optical properties of composites with metallic nanoparticles are studied, taking into account the effects due to the nonlocal dielectric response of the metal and the coalescing of the particles to form clusters. An approach based on various effective medium theories is followed, and the modeling results are compared with those from the cases with local response and particles randomly distributed through the host medium. Possible observations of our modeling results are illustrated via a calculation of the transmission of light through a thin film made of these materials. It is found that the nonlocal effects are particularly significant when the particles coalesce, leading to blue-shifted resonances and slightly lower values in the dielectric functions. The dependence of these effects on the volume fraction and fractal dimension of the metal clusters is studied in detail.

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

International Nuclear Information System (INIS)

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

2008-01-01

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

Discharge ignition near a dielectric

NARCIS (Netherlands)

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

2008-01-01

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

Dielectric properties of PMMA/Soot nanocomposites.

Science.gov (United States)

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

2007-07-01

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

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

Science.gov (United States)

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

2018-05-01

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

Thermally switchable dielectrics

Science.gov (United States)

Dirk, Shawn M.; Johnson, Ross S.

2013-04-30

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

Fabrication of Nonvolatile Memory Effects in High-k Dielectric Thin Films Using Electron Irradiation

International Nuclear Information System (INIS)

Park, Chanrock; Cho, Daehee; Kim, Jeongeun; Hwang, Jinha

2010-01-01

Electron Irradiation can be applied towards nano-floating gate memories which are recognized as one of the next-generation nonvolatile memory semiconductors. NFGMs can overcome the preexisting limitations encountered in Dynamic Random Access Memories and Flash memories with the excellent advantages, i. e. high-density information storage, high response speed, high compactness, etc. The traditional nano-floating gate memories are fabricated through multi-layered nano structures of the dissimilar materials where the charge-trapping portions are sandwiched into the high-k dielectrics. However, this work reports the unique nonvolatile responses in single-layered high-k dielectric thin films if irradiated with highly accelerated electron beams. The implications of the electron irradiation will be discussed towards high-performance nano-floating gate memories

Breakdown of coupling dielectrics for Si microstrip detectors

International Nuclear Information System (INIS)

Candelori, A.; Paccagnella, A.; Padova Univ.; Saglimbeni, G.

1999-01-01

Double-layer coupling dielectrics for AC-coupled Si microstrip detectors have been electrically characterized in order to determine their performance in a radiation-harsh environment, with a focus on the dielectric breakdown. Two different dielectric technologies have been investigated: SiO 2 /TEOS and SiO 2 /Si 3 N 4 . Dielectrics have been tested by using a negative gate voltage ramp of 0.2 MV/(cm·s). The metal/insulator/Si I-V characteristics show different behaviours depending on the technology. The extrapolated values of the breakdown field for unirradiated devices are significantly higher for SiO 2 /Si 3 N 4 dielectrics, but the data dispersion is lower for SiO 2 /TEOS devices. No significant variation of the breakdown field has been measured after a 10 Mrad (Si) γ irradiation for SiO 2 /Si 3 N 4 dielectrics. Finally, the SiO 2 /Si 3 N 4 DC conduction is enhanced if a positive gate voltage ramp is applied with respect to the negative one, due to the asymmetric conduction of the double-layer dielectric

Capacitive Cells for Dielectric Constant Measurement

Science.gov (United States)

Aguilar, Horacio Munguía; Maldonado, Rigoberto Franco

2015-01-01

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

Norbornylene-based polymer systems for dielectric applications

Science.gov (United States)

Dirk, Shawn M [Albuquerque, NM; Wheeler, David R [Albuquerque, NM

2012-07-17

A capacitor having at least one electrode pair being separated by a dielectric component, with the dielectric component being made of a polymer such as a norbornylene-containing polymer with a dielectric constant greater than 3 and a dissipation factor less than 0.1 where the capacitor has an operating temperature greater than 100.degree. C. and less than 170.degree. C.

ac conductivity and dielectric properties of amorphous Se80Te20-xGex chalcogenide glass film compositions

International Nuclear Information System (INIS)

Hegab, N.A.; Afifi, M.A.; Atyia, H.E.; Farid, A.S.

2009-01-01

Thin films of the prepared Se 80 Te 20-x Ge x (x = 5, 7 and 10 at.%) were prepared by thermal evaporation technique. X-ray diffraction patterns showed that the films were in amorphous state. The ac conductivity and dielectric properties of the investigated film compositions were studied in the frequency range 0.1-100 kHz and in temperature range (303-373 K). The experimental results indicated that the ac conductivity and the dielectric properties depended on the temperature and frequency. The ac conductivity is found to obey the ω s law, in accordance with the hopping model, s is found to be temperature dependent (s 1 and dielectric loss ε 2 were found to decrease with frequency and increase with temperature. The maximum barrier height W m , calculated from dielectric measurements according to Guintini equation, agrees with that proposed by the theory of hopping over potential barrier as suggested by Elliott in case of chalcogenide glasses. The density of localized states was estimated for the studied film compositions. The variation of the studied properties with Ge content was also investigated.

Perfect coupling of light to a periodic dielectric/metal/dielectric structure

Science.gov (United States)

Wang, Zhengling; Li, Shiqiang; Chang, R. P. H.; Ketterson, John B.

2014-07-01

Using the finite difference time domain method, it is demonstrated that perfect coupling can be achieved between normally incident light and a periodic dielectric/metal/dielectric structure. The structure serves as a diffraction grating that excites modes related to the long range surface plasmon and short range surface plasmon modes that propagate on continuous metallic films. By optimizing the structural dimensions, perfect coupling is achieved between the incident light and these modes. A high Q of 697 and an accompanying ultrasharp linewidth of 0.8 nm are predicted for a 10 nm silver film for optimal conditions.

AC conductivity and dielectric properties of amorphous GexSb40-xSe60 thin films

International Nuclear Information System (INIS)

Atyia, H.E.; Farid, A.M.; Hegab, N.A.

2008-01-01

Measurements of AC conductivity and dielectric properties have been made for chalcogenide film samples of Ge x Sb 40-x Se 60 (with x=0, 10 and 20 at%) at different temperatures (303-393 K) and various frequencies (10 2 -10 5 Hz). It was found that the AC conductivity obeys the law σ(ω, T)=Aω s . The exponent s 1 and dielectric loss ε 2 were found to decrease with frequency and increase with temperature. The maximum barrier height W M was calculated from dielectric measurements according to the Guintini equation. It was found that the obtained value of W m agrees with that proposed by the theory of hopping of charge carriers over potential barrier as suggested by Elliott in case of chalcogenide glasses. The density of localized states N(E F ) has also been calculated for the studied compositions. The effect of decreasing the Sb content at the expense of the Ge content was investigated for the obtained results of the studied parameters

All-dielectric metamaterial frequency selective surface based on spatial arrangement ceramic resonators

Science.gov (United States)

Li, Liyang; Wang, Jun; Feng, Mingde; Ma, Hua; Wang, Jiafu; Du, Hongliang; Qu, Shaobo

In this paper, we demonstrate a method of designing all-dielectric metamaterial frequency selective surface (FSS) with ceramic resonators in spatial arrangement. Compared with the traditional way, spatial arrangement provides a flexible way to handle the permutation and combination of different ceramic resonators. With this method, the resonance response can be adjusted easily to achieve pass/stop band effects. As an example, a stop band spatial arrangement all-dielectric metamaterial FSS is designed. Its working band is in 11.65-12.23GHz. By adjusting permittivity and geometrical parameters of ceramic resonators, we can easily modulate the resonances, band pass or band stop characteristic, as well as the working band.

Transient change in the shape of premixed burner flame with the superposition of pulsed dielectric barrier discharge

Science.gov (United States)

Zaima, Kazunori; Sasaki, Koichi

2016-08-01

We investigated the transient phenomena in a premixed burner flame with the superposition of a pulsed dielectric barrier discharge (DBD). The length of the flame was shortened by the superposition of DBD, indicating the activation of combustion chemical reactions with the help of the plasma. In addition, we observed the modulation of the top position of the unburned gas region and the formations of local minimums in the axial distribution of the optical emission intensity of OH. These experimental results reveal the oscillation of the rates of combustion chemical reactions as a response to the activation by pulsed DBD. The cycle of the oscillation was 0.18-0.2 ms, which could be understood as the eigenfrequency of the plasma-assisted combustion reaction system.

Hidden symmetries in N-layer dielectric stacks

Science.gov (United States)

Liu, Haihao; Shoufie Ukhtary, M.; Saito, Riichiro

2017-11-01

The optical properties of a multilayer system with arbitrary N layers of dielectric media are investigated. Each layer is one of two dielectric media, with a thickness one-quarter the wavelength of light in that medium, corresponding to a central frequency f 0. Using the transfer matrix method, the transmittance T is calculated for all possible 2 N sequences for small N. Unexpectedly, it is found that instead of 2 N different values of T at f 0 (T 0), there are only (N/2+1) discrete values of T 0, for even N, and (N + 1) for odd N. We explain this high degeneracy in T 0 values by finding symmetry operations on the sequences that do not change T 0. Analytical formulae were derived for the T 0 values and their degeneracies as functions of N and an integer parameter for each sequence we call ‘charge’. Additionally, the bandwidth at f 0 and filter response of the transmission spectra are investigated, revealing asymptotic behavior at large N.

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

Science.gov (United States)

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.

Accelerating Dielectrics Design Using Thinking Machines

Science.gov (United States)

Ramprasad, R.

2013-03-01

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

Water-induced charge transport in tablets of microcrystalline cellulose of varying density: dielectric spectroscopy and transient current measurements

International Nuclear Information System (INIS)

Nilsson, Martin; Alderborn, Goeran; Stroemme, Maria

2003-01-01

Room temperature dielectric frequency response data taken over 13 decades in frequency on microcrystalline cellulose (MCC) tablets of varying density are presented. The frequency response shows on three different processes: the first one is a high-frequency relaxation process whose magnitude increases and reaches a plateau as the tablet density increases. This process is associated with orientational motions of local chain segments via glycosidic bonds. The second relaxation process, related to the presence of water in the MCC matrix, is insensitive to changes in tablet density. At lower frequencies, dc-like imperfect charge transport dominates the dielectric spectrum. The dc conductivity was found to decrease with increasing tablet density and increase exponentially with increasing humidity. Transient current measurements indicated that two different ionic species, protons and OH - ions, lied behind the observed conductivity. At ambient humidity of 22%, only one in a billion of the water molecules present in the tablet matrix participated in long range dc conduction. The diffusion coefficient of the protons and OH - ions were found to be of the order of 10 -9 cm 2 /s, which is the same as for small salt building ions in MCC. This shows that ionic drugs leaving a tablet matrix may diffuse in the same manner as the constituent ions of water and, thus, elucidates the necessity to understand the water transport properties of excipient materials to be able to tailor the drug release process from pharmaceutical tablets

Dielectric relaxation in SrTiO.sub.3./sub.-based solid solutions with heterovalent substitutions

Czech Academy of Sciences Publication Activity Database

Markovin, P.A.; Lemanov, V. V.; Guzhva, M.E.; Trepakov, Vladimír

2014-01-01

Roč. 469, č. 1 (2014), s. 43-49 ISSN 0015-0193 Institutional support: RVO:68378271 Keywords : quantum paraelectric * dielectric relaxation * local charge compensation Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 0.469, year: 2014

Study of high-k gate dielectrics by means of positron annihilation

International Nuclear Information System (INIS)

Uedono, A.; Naito, T.; Otsuka, T.; Ito, K.; Shiraishi, K.; Yamabe, K.; Miyazaki, S.; Watanabe, H.; Umezawa, N.; Hamid, A.; Chikyow, T.; Ohdaira, T.; Suzuki, R.; Ishibashi, S.; Inumiya, S.; Kamiyama, S.; Akasaka, Y.; Nara, Y.; Yamada, K.

2007-01-01

High-dielectric constant (high-k) gate materials, such as HfSiO x and HfAlO x , fabricated by atomic-layer-deposition techniques were characterized using monoenergetic positron beams. Measurements of the Doppler broadening spectra of annihilation radiation and the lifetime spectra of positrons indicated that positrons annihilated from the trapped state by open volumes that exist intrinsically in amorphous structures of the films. The size distributions of the open volumes and the local atomic configurations around such volumes can be discussed using positron annihilation parameters, and they were found to correlate with the electrical properties of the films. We confirmed that the positron annihilation is useful technique to characterize the matrix structure of amorphous high-k materials, and can be used to determine process parameters for the fabrication of high-k gate dielectrics. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Probing dielectric ceramics surface at sub-micrometer scale

Energy Technology Data Exchange (ETDEWEB)

Fiorenza, Patrick; Lo Nigro, Raffaella; Raineri, Vito [Istituto per la Microelettronica e Microsistemi, Consiglio Nazionale delle Ricerche, Stradale Primosole 50, 95121 Catania (Italy); Schmidt, Rainer; Sinclair, Derek C, E-mail: patrick.fiorenza@imm.cnr.it [Department of Engineering Materials, Sir Robert Hadfield Building, University of Sheffield, Mappin Street, Sheffield, S1 3JD (United Kingdom)

2010-02-15

Scanning probe microscopy (SPM) with conductive tips has been used to image the dielectric properties of ceramics with giant permittivity. In particular, measurements in impedance mode of local resistivity allowed to image the permittivity map on polycrystalline materials. Such imaging provides correlation between the dielectric properties and the sample structure, in particular focusing on defects inside the single grains. Great attention has been devoted to the possible artefacts due to surface imperfections, such as huge roughness and/or contamination. A reliable surface investigation has been obtained after the definition of both the physical and geometrical criteria to avoid the artefacts due to both the surface or anomalous tip-sample contact area variation (for instance, in grain boundaries, holes and cracks in the ceramic pills). In particular, the power spectral density (PSD) allows to get access to the different periodic components of the surface roughness. The PSD demonstrated to be a sensitive tool to check the surface conditions after the polishing procedures aimed to the progressive decreasing of surface roughness, in order to reach the SPM limits and to avoid artefacts inducing wrong data interpretation.

Impedance spectroscopic and dielectric analysis of Ba0.7Sr0.3TiO3 thin films

International Nuclear Information System (INIS)

Rouahi, A.; Kahouli, A.; Sylvestre, A.; Defaÿ, E.; Yangui, B.

2012-01-01

Highlights: ► The material exhibits the contribution of both grain and grain boundaries in the electric response of Ba 0.7 Sr 0.3 TiO 3 . ► The plot of normalized complex dielectric modulus and impedance as a function of frequency exhibits both short and long-range conduction in the film. ► The frequency dependence of ac conductivity exhibits a polaron hopping mechanism with activation energy of 0.38 eV. ► The complex dielectric modulus analysis confirmed the presence of a non-Debye type of conductivity relaxation deduced from the KWW function. - Abstract: Polycrystalline Ba 0.7 Sr 0.3 TiO 3 thin film with Pt/BST/Pt/TiO 2 /SiO 2 structure was prepared by ion beam sputtering. The film was post annealed at 700 °C. The dielectric and electric modulus properties were studied by impedance spectroscopy over a wide frequency range [0.1–10 5 Hz] at different temperatures [175–350 °C]. The Nyquist plots (Z″ vs . Z′) show the contribution of both grain and grain boundaries at higher temperature on the electric response of BST thin films. Moreover, the resistance of grains decreases with the rise in temperature and the material exhibits a negative temperature coefficient of resistance. The electric modulus plot indicates the non-Debye type of dielectric relaxation. The values of the activation energy computed from both plots of Z″ and M″ are 0.86 eV and 0.81 eV respectively, which reveals that the species responsible for conduction are the same. The scaling behavior of M ″ /M ″ max shows the temperature independent nature of relaxation time. The plot of normalized complex dielectric modulus and impedance as a function of frequency exhibits both short and long-range conduction in the film.

Hysteresis behaviour of low-voltage organic field-effect transistors employing high dielectric constant polymer gate dielectrics

International Nuclear Information System (INIS)

Kim, Se Hyun; Yun, Won Min; Kwon, Oh-Kwan; Hong, Kipyo; Yang, Chanwoo; Park, Chan Eon; Choi, Woon-Seop

2010-01-01

Here, we report on the fabrication of low-voltage-operating pentacene-based organic field-effect transistors (OFETs) that utilize crosslinked cyanoethylated poly(vinyl alcohol) (CR-V) gate dielectrics. The crosslinked CR-V-based OFET could be operated successfully at low voltages (below 4 V), but abnormal behaviour during device operation, such as uncertainty in the field-effect mobility (μ) and hysteresis, was induced by the slow polarization of moieties embedded in the gate dielectric (e.g. polar functionalities, ionic impurities, water and solvent molecules). In an effort to improve the stability of OFET operation, we measured the dependence of μ and hysteresis on dielectric thickness, CR-V crosslinking conditions and sweep rate of the gate bias. The influence of the CR-V surface properties on μ, hysteresis, and the structural and morphological features of the pentacene layer grown on the gate dielectric was characterized and compared with the properties of pentacene grown on a polystyrene surface.

Homogeneous/Inhomogeneous-Structured Dielectrics and their Energy-Storage Performances.

Science.gov (United States)

Yao, Zhonghua; Song, Zhe; Hao, Hua; Yu, Zhiyong; Cao, Minghe; Zhang, Shujun; Lanagan, Michael T; Liu, Hanxing

2017-05-01

The demand for dielectric capacitors with higher energy-storage capability is increasing for power electronic devices due to the rapid development of electronic industry. Existing dielectrics for high-energy-storage capacitors and potential new capacitor technologies are reviewed toward realizing these goals. Various dielectric materials with desirable permittivity and dielectric breakdown strength potentially meeting the device requirements are discussed. However, some significant limitations for current dielectrics can be ascribed to their low permittivity, low breakdown strength, and high hysteresis loss, which will decrease their energy density and efficiency. Thus, the implementation of dielectric materials for high-energy-density applications requires the comprehensive understanding of both the materials design and processing. The optimization of high-energy-storage dielectrics will have far-reaching impacts on the sustainable energy and will be an important research topic in the near future. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Locally preserved α  →  β phase transition in natural radiation-damaged titanite (CaTiSiO5): evidence from laser-induced photoluminescence and dielectric measurements

Science.gov (United States)

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.

Influence of test capacitor features on piezoelectric and dielectric measurement of ferroelectric films.

Science.gov (United States)

Wang, Zhihong; Lau, Gih Keong; Zhu, Weiguang; Chao, Chen

2006-01-01

This paper presents both theoretical and numerical analyses of the piezoelectric and dielectric responses of a highly idealized film-on-substrate system, namely, a polarized ferroelectric film perfectly bonded to an elastic silicon substrate. It shows that both effective dielectric and piezoelectric properties of the films change with the size and configuration of the test capacitor. There exists a critical electrode size that is smaller than the diameter of the commonly used substrate. The effective film properties converge to their respective constrained values as capacitor size increases to the critical size. If capacitor size is smaller than the critical size, the surface displacement at the top electrode deviates from the net thickness change in response to an applied voltage because the film is deformable at the film/substrate interface. The constrained properties of the films depend only on those of bulk ferroelectrics but are independent of film thickness and substrate properties. The finding of the critical capacitor size together with analytical expressions of the constrained properties makes it possible to realize consistent measurement of piezoelectric and dielectric properties of films. A surface scanning technique is recommended to measure the profile of piezoresponses of the film so that the constrained properties of the film can be identified accurately.

Dielectric response of molecules in empirical tight-binding theory

Science.gov (United States)

Boykin, Timothy B.; Vogl, P.

2002-01-01

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

Localized temperature stability in Low Temperature Cofired Ceramics (LTCC).

Energy Technology Data Exchange (ETDEWEB)

Dai, Steven Xunhu; Hsieh, Lung-Hwa.

2012-04-01

The base dielectrics of commercial low temperature cofired ceramics (LTCC) systems have a temperature coefficient of resonant frequency ({tau}{sub f}) in the range -50 {approx} -80 ppm/C. In this research we explored a method to realize zero or near zero {tau}{sub f} resonators by incorporating {tau}{sub f} compensating materials locally into a multilayer LTCC structure. To select composition for {tau}{sub f} adjustment, {tau}{sub f} compensating materials with different amount of titanates were formulated, synthesized, and characterized. Chemical interactions and physical compatibility between the {tau}{sub f} modifiers and the host LTCC dielectrics were investigated. Studies on stripline (SL) resonator panels with multiple compensating dielectrics revealed that: 1) compositions using SrTiO{sub 3} provide the largest {tau}{sub f} adjustment among titanates, 2) the {tau}{sub f} compensation is proportional to the amount of SrTiO{sub 3} in compensating materials, as well as the thickness of the compensating layer, and 3) the most effective {tau}{sub f} compensation is achieved when the compensating dielectric is integrated next to the SL. Using the effective dielectric constant of a heterogeneous layered dielectric structure, results from Method of Momentum (MoM) electromagnetic simulations are consistent with the experimental observations.

Dielectric material options for integrated capacitors

NARCIS (Netherlands)

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

2014-01-01

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

Investigation of dielectric constant variations for Malaysians soil species towards its natural background dose

Science.gov (United States)

Jafery, Khawarizmi Mohd; Embong, Zaidi; Khee, Yee See; Haimi Dahlan, Samsul; Tajudin, Saiful Azhar Ahmad; Ahmad, Salawati; Kudnie Sahari, Siti; Maxwell, Omeje

2018-01-01

The correlation of natural background gamma radiation and real part of the complex relative permittivity (dielectric constant) for various species Malaysian soils was investigated in this research. The sampling sites were chosen randomly according to soils groups that consist of sedentary, alluvial and miscellaneous soil which covered the area of Batu Pahat, Kluang and Johor Bahru, Johor state of Malaysia. There are 11 types of Malaysian soil species that have been studied; namely Peat, Linau-Sedu, Selangor-Kangkong, Kranji, Telemong-Akob-Local Alluvium, Holyrood-Lunas, Batu Anam-Melaka-Tavy, Harimau Tampoi, Kulai-Yong Peng, Rengam-Jerangau, and Steepland soils. In-situ exposure rates of each soil species were measured by using portable gamma survey meter and ex-situ analysis of real part of relative permittivity was performed by using DAK (Dielectric Assessment Kit assist by network analyser). Results revealed that the highest and the lowest background dose rate were 94 ± 26.28 μR hr-1 and 7 ± 0.67 μR hr-1 contributed by Rengam Jerangau and Peat soil species respectively. Meanwhile, dielectric constant measurement, it was performed in the range of frequency between 100 MHz to 3 GHz. The measurements of each soils species dielectric constant are in the range of 1 to 3. At the lower frequencies in the range of 100 MHz to 600 MHz, it was observed that the dielectric constant for each soil species fluctuated and inconsistent. But it remained consistent in plateau form of signal at higher frequency at range above 600 MHz. From the comparison of dielectric properties of each soil at above 600 MHz of frequency, it was found that Rengam-Jerangau soil species give the highest reading and followed by Selangor-Kangkong species. The average dielectric measurement for both Selangor-Kangkong and Rengam-Jerangau soil species are 2.34 and 2.35 respectively. Meanwhile, peat soil species exhibits the lowest dielectric measurement of 1.83. It can be clearly seen that the pattern

Dielectric behaviour and a.c. conductivity in CuxFe3–xO4 ferrite

Indian Academy of Sciences (India)

Unknown

frequency on the dielectric behaviour and a.c. electrical conductivity offers valuable information about conduction phenomenon in ferrites based on localized electric charge carriers (El Hitti 1996). The d.c. electrical conductivity and thermoelectric power have already been studied for copper ferrite (Patil et al 1994), while a.c. ...

Dielectric Properties of PANI/CuO Nanocomposites

Science.gov (United States)

Ambalagi, Sharanabasamma M.; Devendrappa, Mahalesh; Nagaraja, Sannakki; Sannakki, Basavaraja

2018-02-01

The combustion method is used to prepare the Copper Oxide (CuO) nanoparticles. The nanocomposites of Polyaniline (PANI) by doping with copper oxide nanoparticles have synthesized at 10, 20, 30, 40 and 50 different weight percentages during the in-situ polymerization. The samples of nanocomposite of PANI-CuO were characterized by using X-Ray diffraction (XRD) technique. The physical properties such as dielectric constant, dielectric loss and A C conductivity of the nanocomposites are studied as a function of frequency in the range 5Hz-35MHz at room temperature. It is found that the dielectric constant decreases as the frequency increases. The dielectric constant it remains constant at higher frequencies and it is also observed that in particular frequency both the dielectric constant and dielectric loss are decreased as a weight percentage of CuO increased. In case of AC conductivity it is found that as the frequency increases the AC conductivity remains constant up to 3.56MHz and afterwards it increases as frequency increases. This is due to the increase in charge carriers through the hopping mechanism in the polymer nanocomposites. It is also observed that as a weight percentage of CuO increased the AC conductivity is also increasing at a particular frequency.

Dielectric silicone elastomers with mixed ceramic nanoparticles

International Nuclear Information System (INIS)

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

2015-01-01

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

Dielectric silicone elastomers with mixed ceramic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

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

2015-11-15

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

Dielectric loss against piezoelectric power harvesting

Science.gov (United States)

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

2014-09-01

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

Dielectric loss against piezoelectric power harvesting

International Nuclear Information System (INIS)

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

2014-01-01

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

Elaboration and dielectric characterization of a doped ferroelectric ...

African Journals Online (AJOL)

... 1150,1180 and 1200 °C successively to optimize the sintering temperature optimal where the density of the sample is maximum (near theoretical density) and therefore the product has better physical quality. The study of dielectric properties of all samples showed a high permittivity dielectric εr = 18018, low dielectric loss: ...

Note: On the dielectric constant of nanoconfined water

OpenAIRE

Zhang, Chao

2018-01-01

Investigations of dielectric properties of water in nanoconfinement are highly relevant for various applications. Here, using a simple capacitor model, we show that the low dielectric constant of nanoconfined water found in molecular dynamics simulations can be largely explained by the so-called dielectric dead-layer effect known for ferroelectric nanocapacitors.

Electrode/Dielectric Strip For High-Energy-Density Capacitor

Science.gov (United States)

Yen, Shiao-Ping S.

1994-01-01

Improved unitary electrode/dielectric strip serves as winding in high-energy-density capacitor in pulsed power supply. Offers combination of qualities essential for high energy density: high permittivity of dielectric layers, thinness, and high resistance to breakdown of dielectric at high electric fields. Capacitors with strip material not impregnated with liquid.

Dielectric measurements on PWB materials at microwave frequencies

Indian Academy of Sciences (India)

Unknown

the angular frequency and c0 the velocity of light, c the thickness of the ... Dielectric parameters, absorption index and refractive index for pure PSF and pure PMMA at 8⋅92 GHz frequency and at 35°C temperature. Dielectric. Dielectric. Loss. Relaxation. Conductivity Absorption. Refractive. Thickness, constant loss tangent.

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

Science.gov (United States)

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.

Radiation pressure on a dielectric surface

International Nuclear Information System (INIS)

Hirose, A.

2010-01-01

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

High thermal conductivity lossy dielectric using co-densified multilayer configuration

Science.gov (United States)

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

2003-06-17

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

Structural, magnetic and dielectric investigations in antimony doped nano-phased nickel-zinc ferrites

Energy Technology Data Exchange (ETDEWEB)

Lakshmi, Ch.S. [Department of Physics, Regency Institute of Technology, Adivipolam Yanam 533464, Pondicherry (India); Sridhar, Ch.S.L.N. [Department of Physics, Vignana Bharathi Institute of Technology, Aushapur(v) Ghatkesar (M), Hyderabad 501301, Telangana (India); Govindraj, G. [Department of Physics, School of Physical, Chemical and Applied Sciences, Pondicherry University, R.V.Nagar, Kalapet, Pondicherry 605014 (India); Bangarraju, S. [Department of Physics, Andhra University, Visakhapatnam 530003, Andhrapradesh (India); Potukuchi, D.M., E-mail: potukuchidm@yahoo.com [Department of Physics, University College of Engineering, Jawaharlal Nehru Technological University:Kakinada, Kakinada 533003 (India)

2015-02-15

Nanocrystalline Ni–Zn–Sb ferrites synthesized by hydrothermal method are reported. Influence of Sb{sup 5+} ions on structural, magnetic and dielectric properties of ferrites is studied. Phase identification, lattice parameter and crystallite size studies are carried out using by X-ray diffraction (XRD). Addition of dopant resulted for decrease in lattice parameter. Crystallite size gets reduced from 62 nm to 38 nm with doping of Antimony. Crystallite size and porosity exhibit similar trends with doping. Morphological study is carried out by Field Emission Scanning Electron Microscopy (FESEM). Strong FTIR absorption bands at 400–600 cm{sup −1} confirm the formation of ferrite structure. Increase of porosity is attributed to the grain size. Doping with Antimony results for decrease in saturation magnetization and increase in coercivity. An initial increase of saturation magnetization for x=0.1 is attributed to the unusually high density. Reversed trend of coercivity with crystallite size are observed. Higher value of dielectric constant ε′(ω) is attributed to the formation of excess of Fe{sup 2+} ions caused by aliovalent doping of Sb{sup 5+} ions. Variation of dielectric constant infers hopping type of conductivity mechanism. The dielectric loss factor tanδ attains lower values of ∼10{sup −2}. High ac resistivity ρ(ω) of 10{sup 8} Ω cm is witnessed for antimony doped ferrites. Higher saturation magnetization and enhanced dielectric response directs for a possible utility as microwave oscillators and switches.

Model-based synthesis of locally contingent responses to global market signals

Science.gov (United States)

Magliocca, N. R.

2015-12-01

Rural livelihoods and the land systems on which they depend are increasingly influenced by distant markets through economic globalization. Place-based analyses of land and livelihood system sustainability must then consider both proximate and distant influences on local decision-making. Thus, advancing land change theory in the context of economic globalization calls for a systematic understanding of the general processes as well as local contingencies shaping local responses to global signals. Synthesis of insights from place-based case studies of land and livelihood change is a path forward for developing such systematic knowledge. This paper introduces a model-based synthesis approach to investigating the influence of local socio-environmental and agent-level factors in mediating land-use and livelihood responses to changing global market signals. A generalized agent-based modeling framework is applied to six case-study sites that differ in environmental conditions, market access and influence, and livelihood settings. The largest modeled land conversions and livelihood transitions to market-oriented production occurred in sties with relatively productive agricultural land and/or with limited livelihood options. Experimental shifts in the distributions of agents' risk tolerances generally acted to attenuate or amplify responses to changes in global market signals. Importantly, however, responses of agents at different points in the risk tolerance distribution varied widely, with the wealth gap growing wider between agents with higher or lower risk tolerance. These results demonstrate model-based synthesis is a promising approach to overcome many of the challenges of current synthesis methods in land change science, and to identify generalized as well as locally contingent responses to global market signals.

Significantly Elevated Dielectric and Energy Storage Traits in Boron Nitride Filled Polymer Nano-composites with Topological Structure

Science.gov (United States)

Feng, Yefeng; Zhang, Jianxiong; Hu, Jianbing; Li, Shichun; Peng, Cheng

2018-03-01

Interface induced polarization has a prominent influence on dielectric properties of 0-3 type polymer based composites containing Si-based semi-conductors. The disadvantages of composites were higher dielectric loss, lower breakdown strength and energy storage density, although higher permittivity was achieved. In this work, dielectric, conductive, breakdown and energy storage properties of four nano-composites have been researched. Based on the cooperation of fluoropolymer/alpha-SiC layer and fluoropolymer/hexagonal-BN layer, it was confirmed constructing the heterogeneous layer-by-layer composite structure rather than homogeneous mono-layer structure could significantly reduce dielectric loss, promote breakdown strength and increase energy storage density. The former worked for a larger dielectric response and the latter layer acted as a robust barrier of charge carrier transfer. The best nano-composite could possess a permittivity of 43@100 Hz ( 3.3 times of polymer), loss of 0.07@100 Hz ( 37% of polymer), discharged energy density of 2.23 J/cm3@249 kV/cm ( 10 times of polymer) and discharged energy efficiency of 54%@249 kV/cm ( 5 times of polymer). This work might enlighten a facile route to achieve the promising high energy storage composite dielectrics by constructing the layer-by-layer topological structure.

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

International Nuclear Information System (INIS)

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

2011-01-01

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

Epoxy matrix with triaromatic mesogenic unit in dielectric spectroscopy observation

Science.gov (United States)

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

2018-04-01

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

Ion transport study in polymer-nanocomposite films by dielectric spectroscopy and conductivity scaling

Energy Technology Data Exchange (ETDEWEB)

Tripathi, Namrata, E-mail: ntripat@ilstu.edu [Department of Physics, Illinois State University, Normal, IL 61790 (United States); Thakur, Awalendra K. [Department of Physics, Indian Institute of Technology Patna, Bihar 800013 (India); Shukla, Archana [Department of Metallurgical Engineering & Materials Science, Indian Institute of Technology, Bombay 721302 (India); Marx, David T. [Department of Physics, Illinois State University, Normal, IL 61790 (United States)

2015-07-15

The dielectric and conductivity response of polymer nanocomposite electrolytes (films of PMMA{sub 4}LiClO{sub 4} dispersed with nano-CeO{sub 2} powder) have been investigated. The dielectric behavior was analyzed via the dielectric permittivity (ε′) and dissipation factor (tan δ) of the samples. The analysis has shown the presence of space charge polarization at lower frequencies. The real part of ac conductivity spectra of materials obeys the Jonscher power law. Parameters such as dc conductivity, hopping rate, activation energies and the concentration of charge carriers were determined from conductivity data using the Almond West formalism. It is observed that the higher ionic conductivity at higher temperature is due to increased thermally-activated hopping rates accompanied by a significant increase in carrier concentration. The contribution of carrier concentration to the total conductivity is also confirmed from activation energy of migration conduction and from Summerfield scaling. The ac conductivity results are also well correlated with TEM results.

Ion transport study in polymer-nanocomposite films by dielectric spectroscopy and conductivity scaling

Science.gov (United States)

Tripathi, Namrata; Thakur, Awalendra K.; Shukla, Archana; Marx, David T.

2015-07-01

The dielectric and conductivity response of polymer nanocomposite electrolytes (films of PMMA4LiClO4 dispersed with nano-CeO2 powder) have been investigated. The dielectric behavior was analyzed via the dielectric permittivity (ε‧) and dissipation factor (tan δ) of the samples. The analysis has shown the presence of space charge polarization at lower frequencies. The real part of ac conductivity spectra of materials obeys the Jonscher power law. Parameters such as dc conductivity, hopping rate, activation energies and the concentration of charge carriers were determined from conductivity data using the Almond West formalism. It is observed that the higher ionic conductivity at higher temperature is due to increased thermally-activated hopping rates accompanied by a significant increase in carrier concentration. The contribution of carrier concentration to the total conductivity is also confirmed from activation energy of migration conduction and from Summerfield scaling. The ac conductivity results are also well correlated with TEM results.

Organic dielectrics in high voltage cables

Energy Technology Data Exchange (ETDEWEB)

Vermeer, J

1962-03-01

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

Investigation of dielectric behavior of the PVC/BaTiO3 composite in low-frequencies

Science.gov (United States)

Berrag, A.; Belkhiat, S.; Madani, L.

2018-04-01

Polyvinyl chloride (PVC) is widely used as insulator in electrical engineering especially as cable insulation sheaths. In order to improve the dielectric properties, polymers are mixed with ceramics. In this paper, PVC composites with different weight percentages 2 wt.%, 5 wt.%, 8 wt.% and 10 wt.% were prepared and investigated. Loss index (𝜀″) and dielectric constant (𝜀‧) have been measured using an impedance analyzer RLC. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX) have been used as characterization techniques. The incorporation of BaTiO3 does not modify the crystallinity and the morphology of the PVC but reduces the space charges, therefore the dielectric losses. The frequency response analysis has been followed in the frequency ranges (20-140 Hz and 115-1 MHz). Relaxation frequencies have been evaluated in each frequency range. Experimental measurements have been validated using Cole-Cole’s model. Experimental results show well that BaTiO3 as a filler improves the dielectric properties of PVC.

Thermodynamics and instability of dielectric elastomer (Conference Presentation)

Science.gov (United States)

Liu, Liwu; Liu, Yanju; Leng, Jinsong; Mu, Tong

2017-04-01

Dielectric elastomer is a kind of typical soft active material. It can deform obviously when subjected to an external voltage. When a dielectric elastomer with randomly oriented dipoles is subject to an electric field, the dipoles will rotate to and align with the electric field. The polarization of the dielectric elastomer may be saturated when the voltage is high enough. When subjected to a mechanical force, the end-to-end distance of each polymer chain, which has a finite contour length, will approach the finite value, reaching a limiting stretch. On approaching the limiting stretch, the elastomer stiffens steeply. Here, we develop a thermodynamic constitutive model of dielectric elastomers undergoing polarization saturation and strain-stiffening, and then investigate the stability (electromechanical stability, snap-through stability) and voltage induced deformation of dielectric elastomers. Analytical solution has been obtained and it reveals the marked influence of the extension limit and polarization saturation limit on its instability. The developed thermodynamic constitutive model and simulation results would be helpful in future to the research of dielectric elastomer based high-performance transducers.

Local and global responses in complex gene regulation networks

Science.gov (United States)

Tsuchiya, Masa; Selvarajoo, Kumar; Piras, Vincent; Tomita, Masaru; Giuliani, Alessandro

2009-04-01

An exacerbated sensitivity to apparently minor stimuli and a general resilience of the entire system stay together side-by-side in biological systems. This apparent paradox can be explained by the consideration of biological systems as very strongly interconnected network systems. Some nodes of these networks, thanks to their peculiar location in the network architecture, are responsible for the sensitivity aspects, while the large degree of interconnection is at the basis of the resilience properties of the system. One relevant feature of the high degree of connectivity of gene regulation networks is the emergence of collective ordered phenomena influencing the entire genome and not only a specific portion of transcripts. The great majority of existing gene regulation models give the impression of purely local ‘hard-wired’ mechanisms disregarding the emergence of global ordered behavior encompassing thousands of genes while the general, genome wide, aspects are less known. Here we address, on a data analysis perspective, the discrimination between local and global scale regulations, this goal was achieved by means of the examination of two biological systems: innate immune response in macrophages and oscillating growth dynamics in yeast. Our aim was to reconcile the ‘hard-wired’ local view of gene regulation with a global continuous and scalable one borrowed from statistical physics. This reconciliation is based on the network paradigm in which the local ‘hard-wired’ activities correspond to the activation of specific crucial nodes in the regulation network, while the scalable continuous responses can be equated to the collective oscillations of the network after a perturbation.

Dielectric Optical Antenna Emitters and Metamaterials

Science.gov (United States)

Schuller, Jon

2009-03-01

Optical antennas are critical components in nanophotonics research due to their unparalleled ability to concentrate electromagnetic energy into nanoscale volumes. Researchers typically construct such antennas from wavelength-size metallic structures. However, recent research has begun to exploit the scattering resonances of high-permittivity particles to realize all-dielectric optical antennas, emitters, and metamaterials. In this talk, we experimentally and theoretically characterize the resonant modes of subwavelength rod-shaped dielectric particles and demonstrate their use in negative index metamaterials and novel infrared light emitters. At mid-infrared frequencies, Silicon Carbide (SiC) is an ideal system for studying the behavior of dielectric optical antennas. At frequencies below the TO phonon resonance, SiC behaves like a dielectric with very large refractive index. Using infrared spectroscopy and analytical Mie calculations we show that individual rod-shaped SiC particles exhibit a multitude of resonant modes. Detailed investigations of these SiC optical antennas reveal a wealth of new physics and applications. We discuss the distinct electromagnetic field profile for each mode, and demonstrate that two of the dielectric-type Mie resonances can be combined in a particle array to form a negative index metamaterial [1]. We further show that these particles can serve as ``broadcasting'' antennas. Using a custom-built thermal emission microscope we collect emissivity spectra from single SiC particles at elevated temperatures, highlighting their use as subwavelength resonant light emitters. Finally, we derive and verify a variety of general analytical results applicable to all cylindrical dielectric antennas and discuss extensions of the demonstrated concepts to different materials systems and frequency regimes. [1] J.A. Schuller, et al., Phys. Rev. Lett. 99, 107401 (2007)

Dielectric properties of carbon nanotubes/epoxy composites.

Science.gov (United States)

Peng, Jin-Ping; Zhang, Hui; Tang, Long-Cheng; Jia, Yu; Zhang, Zhong

2013-02-01

Material with high dielectric properties possesses the effect of energy storage and electric field homogenization, which plays an important role in the electrical and electronics domain, especially in the capacitor, electrical machinery and cable realm. In this paper, epoxy-based nanocomposites with high dielectric constant were fabricated by adding pristine and ozone functionalized multi-wall carbon nanotubes (MWCNTs). In the process-related aspect, the favorable technological parameter was obtained via reasonable arrangement and consideration of the dispersing methods including high-speed stirring and three-roller mill. As a result, a uniform dispersion status of MWCNTs in matrix has been guaranteed, which was observed by scanning and transmission electron microscopy. Meanwhile, the influence of different MWCNTs contents and diverse frequencies on the dielectric properties was compared. It was found that the dielectric constant of nano-composites decreased gradually with the increasing of frequency (10(3)-10(6) Hz). Moreover, as the content of MWCNTs increasing, the dielectric constant reached to a maximum of about 1,328 at 10(3) Hz when the pristine MWCNTs content was 0.5 wt.%. Accordingly, the DC conductivity results could interpret the peak value phenomenon by percolation threshold of MWCNTs. In addition, at the fixed content, the dielectric constant of epoxy-based nano-composites with ozone functionalized MWCNTs was lower than that of pristine ones.

Ion association at discretely-charged dielectric interfaces: Giant charge inversion

Science.gov (United States)

Wang, Zhi-Yong; Wu, Jianzhong

2017-07-01

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

All-optically tunable EIT-like dielectric metasurfaces hybridized with thin phase change material layers

Science.gov (United States)

Petronijevic, Emilija; Sibilia, Concita

2017-05-01

Electromagnetically induced transparency (EIT), a pump-induced narrow transparency window within the absorption region of a probe, had offered new perspectives in slow-light control in atomic physics. For applications in nanophotonics, the implementation on chip-scaled devices has later been obtained by mimicking this effect by metallic metamaterials. High losses in visible and near infrared range of metal-based metamaterialls have recently opened a new field of all-dielectric metamaterials; a proper configuration of high refractive index dielectric nanoresonators can mimick this effect without losses to get high Q, slow-light response. The next step would be the ability to tune their optical response, and in this work we investigate thin layers of phase change materials (PCM) for all-optical control of EIT-like all-dielectric metamaterials. PCM can be nonvolatively and reversibly switched between two stable phases that differ in optical properties by applying a visible laser pulse. The device is based on Si nanoresonators covered by a thin layer of PCM GeTe; optical and transient thermal simulations have been done to find and optimize the fabrication parameters and switching parameters such as the intensity and duration of the pulse. We have found that the EIT-like response can be switched on and off by applying the 532nm laser pulse to change the phase of the upper GeTe layer. We strongly believe that such approach could open new perspectives in all-optically controlled slow-light metamaterials.

Aging of Dielectric Properties below Tg

DEFF Research Database (Denmark)

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

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

The Electrical Breakdown of Thin Dielectric Elastomers

DEFF Research Database (Denmark)

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

2014-01-01

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

Plane-wave diffraction by periodic structures with artificial anisotropic dielectrics

International Nuclear Information System (INIS)

Kazerooni, Azadeh Semsar; Shahabadi, Mahmoud

2010-01-01

Periodic structures with artificial anisotropic dielectrics are studied. The artificial anisotropic dielectric material in this work is made of two alternating isotropic dielectric layers. By a proper choice of the dielectric constant of the layers, we can realize a uniaxial anisotropic medium with controllable anisotropy. The artificial anisotropic dielectric is then used in periodic structures. For these structures, the optical axis of the artificial dielectric is assumed to be parallel or perpendicular to the period of the structure. Diffraction of plane waves by these structures is analyzed by a fully vectorial rigorous matrix method based on a generalized transmission line (TL) formulation. The propagation constants and field distributions are computed and diffraction properties of such structures are studied to show that, by a proper choice of structural parameters, these periodic structures with artificial anisotropic dielectrics can be used as polarizers or polarizing mirrors

Inverse scattering of a layered and dispersionless dielectric half-space - 1. reflection data from plane waves at normal incidence

International Nuclear Information System (INIS)

Coen, S.

1981-01-01

The theory given by Moses and deRidder is modified so that the derivative of the solution of the Gelfand-Levitan integral equation is not required. Based on this modification, a numerical procedure is developed which approximately constructs the dielectric profile of the layered half-space from the impulse response. Moreover, an inverse scattering theory is developed for a Goupillaud-type dielectric medium, and a fast numerical procedure based on the Berryman and Greene algorithm is presented. The performance of the numerical algorithms is examined by applying them to pecise and imprecise artificial impulse response data. 11 refs

Dielectric-filled radiofrequency linacs

Energy Technology Data Exchange (ETDEWEB)

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

1997-12-31

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

Dielectric lattice gauge theory

International Nuclear Information System (INIS)

Mack, G.

1983-06-01

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

Dielectric lattice gauge theory

International Nuclear Information System (INIS)

Mack, G.

1984-01-01

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

Electrical characterization of microdischarges produced by dielectric barrier discharge in dry air at atmospheric pressure

International Nuclear Information System (INIS)

Jidenko, N; Petit, M; Borra, J P

2006-01-01

This work addresses the case of millimetre sized plane-to-plane dielectric barrier discharge with sinusoidal voltage between 1 and 60 kHz for different configurations in air at atmospheric pressure. The first aim of this work is to achieve a representative statistical analysis of the electrical characteristics of the microdischarges. The numerical data treatment presented here enables us to determine the maximum current, the duration, the amount of charge and the triggering voltage for each current pulse. Both the average values as well as the deviations are checked. The relative influence of the operating parameters (voltage, gas flow rate, gap width, frequency) on the local surface polarization, electron attachment and temperature affecting microdischarge characteristics has been depicted in different arrangements. A special attention is paid to the influence of dielectric walls inside the discharge gap, perpendicular to the electrodes. Besides, this study allows the identification of the operating conditions for which all the microdischarges can be considered identical to study the local physical and chemical processes around each microdischarge

Electrical characterization of microdischarges produced by dielectric barrier discharge in dry air at atmospheric pressure

Energy Technology Data Exchange (ETDEWEB)

Jidenko, N [Laboratoire de Physique des Gaz et des Plasmas (CNRS-Universite Paris XI), Equipe Decharges Electriques et Environnement, Supelec, 91190 Gif sur Yvette (France); Petit, M [Service Electrotechnique et Electronique Industrielle, SUPELEC Plateau de Moulon, 91192 Gif sur Yvette Cedex (France); Borra, J P [Laboratoire de Physique des Gaz et des Plasmas (CNRS-Universite Paris XI), Equipe Decharges Electriques et Environnement, Supelec, 91190 Gif sur Yvette (France)

2006-01-21

This work addresses the case of millimetre sized plane-to-plane dielectric barrier discharge with sinusoidal voltage between 1 and 60 kHz for different configurations in air at atmospheric pressure. The first aim of this work is to achieve a representative statistical analysis of the electrical characteristics of the microdischarges. The numerical data treatment presented here enables us to determine the maximum current, the duration, the amount of charge and the triggering voltage for each current pulse. Both the average values as well as the deviations are checked. The relative influence of the operating parameters (voltage, gas flow rate, gap width, frequency) on the local surface polarization, electron attachment and temperature affecting microdischarge characteristics has been depicted in different arrangements. A special attention is paid to the influence of dielectric walls inside the discharge gap, perpendicular to the electrodes. Besides, this study allows the identification of the operating conditions for which all the microdischarges can be considered identical to study the local physical and chemical processes around each microdischarge.

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

Indian Academy of Sciences (India)

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

Evaluation of Dielectric-Barrier-Discharge Actuator Substrate Materials

Science.gov (United States)

Wilkinson, Stephen P.; Siochi, Emilie J.; Sauti, Godfrey; Xu, Tian-Bing; Meador, Mary Ann; Guo, Haiquan

2014-01-01

A key, enabling element of a dielectric barrier discharge (DBD) actuator is the dielectric substrate material. While various investigators have studied the performance of different homogeneous materials, most often in the context of related DBD experiments, fundamental studies focused solely on the dielectric materials have received less attention. The purpose of this study was to conduct an experimental assessment of the body-force-generating performance of a wide range of dielectric materials in search of opportunities to improve DBD actuator performance. Materials studied included commonly available plastics and glasses as well as a custom-fabricated polyimide aerogel. Diagnostics included static induced thrust, electrical circuit parameters for 2D surface discharges and 1D volume discharges, and dielectric material properties. Lumped-parameter circuit simulations for the 1D case were conducted showing good correspondence to experimental data provided that stray capacitances are included. The effect of atmospheric humidity on DBD performance was studied showing a large influence on thrust. The main conclusion is that for homogeneous, dielectric materials at forcing voltages less than that required for streamer formation, the material chemical composition appears to have no effect on body force generation when actuator impedance is properly accounted for.

Engineering electric and magnetic dipole coupling in arrays of dielectric nanoparticles

Science.gov (United States)

Li, Jiaqi; Verellen, Niels; Van Dorpe, Pol

2018-02-01

Dielectric nanoparticles with both strong electric and magnetic dipole (ED and MD) resonances offer unique opportunities for efficient manipulation of light-matter interactions. Here, based on numerical simulations, we show far-field diffractive coupling of the ED and MD modes in a periodic rectangular array. By using unequal periodicities in the orthogonal directions, each dipole mode is separately coupled and strongly tuned. With this method, the electric and magnetic response of the dielectric nanoparticles can be deliberately engineered to accomplish various optical functionalities. Remarkably, an ultra-sharp MD resonance with sub-10 nm linewidth is achieved with a large enhancement factor for the magnetic field intensity on the order of ˜103. Our results will find useful applications for the detection of chemical and biological molecules as well as the design of novel photonic metadevices.

All-optical tuning of EIT-like dielectric metasurfaces by means of chalcogenide phase change materials.

Science.gov (United States)

Petronijevic, E; Sibilia, C

2016-12-26

Electromagnetically induced transparency (EIT) is a pump-induced narrowband transparency window within an absorption line of the probe beam spectrum in an atomic system. In this paper we propose a way to bring together the all-dielectric metamaterials to have EIT-like effects and to optically tune the response by hybridizing them with a layer of a phase change material. We propose a design of the metamaterial based on Si nanoresonators that can support an EIT-like resonant response. On the top of the resonators we consider a thin layer of a chalcogenide phase change material, which we will use to tune the optical response. Our choice is Ge2Sb2Te5 (GST), since it has two stable phases at room temperature, namely amorphous and crystalline, between which it can be switched quickly, nonvolatively and reversibly, sustaining a large number of switching cycles. They differ in optical properties, while still having moderately low losses in telecom range. Since such dielectric resonators do not have non-radiative losses of metals around 1550nm, they can lead to a high-Q factor of the EIT-like response in this range. Firstly, we optimize the starting structure so that it gives an EIT-like response at 1550 nm when the GST layer is in the amorphous state. Our starting design uses glass as a substrate, but we also consider implementation in SOI technology. If we then switch the thin layer of GST to its crystalline phase, which has higher losses, the EIT-like response is red shifted, providing around 10:1 contrast at 1550nm. This reversible tuning can be done with an ns visible pulsed laser. We discuss the results of the simulation of the dielectric metasurface for different configurations and the tuning possibility.

Theory of radiation pressure on magneto–dielectric materials

International Nuclear Information System (INIS)

Barnett, Stephen M; Loudon, Rodney

2015-01-01

We present a classical linear response theory for a magneto–dielectric material and determine the polariton dispersion relations. The electromagnetic field fluctuation spectra are obtained and polariton sum rules for their optical parameters are presented. The electromagnetic field for systems with multiple polariton branches is quantized in three dimensions and field operators are converted to 1–dimensional forms appropriate for parallel light beams. We show that the field–operator commutation relations agree with previous calculations that ignored polariton effects. The Abraham (kinetic) and Minkowski (canonical) momentum operators are introduced and their corresponding single–photon momenta are identified. The commutation relations of these and of their angular analogues support the identification, in particular, of the Minkowski momentum with the canonical momentum of the light. We exploit the Heaviside–Larmor symmetry of Maxwell’s equations to obtain, very directly, the Einsetin–Laub force density for action on a magneto–dielectric. The surface and bulk contributions to the radiation pressure are calculated for the passage of an optical pulse into a semi–infinite sample. (paper)

Immune Response Augmentation in Metastasized Breast Cancer by Localized Therapy Utilizing Biocompatible Magnetic Fluids

Science.gov (United States)

2008-08-01

SUBJECT TERMS Cancer therapy by localized immune response, Magneto -rehological Fluids 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT...Metastasized Breast Cancer by Localized Therapy utilizing Biocompatible Magnetic Fluids PRINCIPAL INVESTIGATOR: Cahit Evrensel...2008 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Immune Response Augmentation in Metastasized Breast Cancer by Localized Therapy utilizing

Observation of modified radiative properties of cold atoms in vacuum near a dielectric surface

International Nuclear Information System (INIS)

Ivanov, V V; Cornelussen, R A; Heuvell, H B van Linden van den; Spreeuw, R J C

2004-01-01

We have observed a distance-dependent absorption linewidth of cold 87 Rb atoms close to a dielectric-vacuum interface. This is the first observation of modified radiative properties in vacuum near a dielectric surface. A cloud of cold atoms was created using a magneto-optical trap (MOT) and optical molasses cooling. Evanescent waves (EW) were used to observe the behaviour of the atoms near the surface. We observed an increase of the absorption linewidth by up to 25% with respect to the free-space value. Approximately half the broadening can be explained by cavity quantum electrodynamics (CQED) as an increase of the natural linewidth and inhomogeneous broadening. The remainder we attribute to local Stark shifts near the surface. By varying the characteristic EW length we have observed a distance dependence characteristic for CQED

Quantum optics of dispersive dielectric media

International Nuclear Information System (INIS)

Lenac, Z.

2003-01-01

We quantize the electromagnetic field in a polar medium starting with the fundamental equations of motion. In our model the medium is described by a Lorenz-type dielectric function ε(r,ω) appropriate, e.g., for ionic crystals, metals, and inert dielectrics. There are no restrictions on the spatial behavior of the dielectric function, i.e., there can be many different polar media with arbitrary shapes. We assume no losses in our system so the dielectric function for the whole space is assumed as real. The quantization procedure is based on an expansion of the total field (transverse and longitudinal) in terms of the coupled (polariton) eigenmodes, and this approach incorporates all previous results derived for similar but restricted systems (e.g., without spatial or frequency dependence of coupled modes). Within the same model, we also quantize the Hamiltonian of a nonretarded electromagnetic field in polar media. Particular attention is paid to the derivation of the orthogonality and closure relations, which are used in a discussion of the fundamental (equal-time) commutation relations between the conjugate field operators

Dielectric optical antenna thermal emitters and metamaterials

Science.gov (United States)

Schuller, Jonathan Aaron

Optical antennas are critical components in nanophotonics research due to their unparalleled ability to concentrate electromagnetic energy into nanoscale volumes. Researchers typically construct such antennas from wavelength-size metallic structures. However, recent research has begun to exploit the scattering resonances of high-permittivity particles to realize all-dielectric optical antennas, emitters, and metamaterials. In this thesis, we experimentally and theoretically characterize the resonant modes of subwavelength rod-shaped dielectric particles and demonstrate their use in negative index metamaterials and novel infrared light emitters. At mid-infrared frequencies, Silicon Carbide (SiC) is an ideal system for studying the behavior of dielectric optical antennas. At frequencies below the TO phonon resonance, SiC behaves like a dielectric with very large refractive index. Using infrared spectroscopy and analytical Mie calculations we show that individual rod-shaped SiC particles exhibit a multitude of resonant modes. Detailed investigations of these SiC optical antennas reveal a wealth of new physics and applications. We discuss the distinct electromagnetic field profile for each mode, and demonstrate that two of the dielectric-type Mie resonances can be combined in a particle array to form a negative index metamaterial. We further show that these particles can serve as "broadcasting" antennas. Using a custom-built thermal emission microscope we collect emissivity spectra from single SiC particles at elevated temperatures, highlighting their use as subwavelength resonant light emitters. Finally, we derive and verify a variety of general analytical results applicable to all cylindrical dielectric antennas.

On dielectric breakdown statistics

International Nuclear Information System (INIS)

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

2006-01-01

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

Numerical study of the influence of dielectric tube on propagation of atmospheric pressure plasma jet based on coplanar dielectric barrier discharge

Science.gov (United States)

Haixin, HU; Feng, HE; Ping, ZHU; Jiting, OUYANG

2018-05-01

A 2D fluid model was employed to simulate the influence of dielectric on the propagation of atmospheric pressure helium plasma jet based on coplanar dielectric barrier discharge (DBD). The spatio-temporal distributions of electron density, ionization rate, electrical field, spatial charge and the spatial structure were obtained for different dielectric tubes that limit the helium flow. The results show that the change of the relative permittivity of the dielectric tube where the plasma jet travels inside has no influence on the formation of DBD itself, but has great impact on the jet propagation. The velocity of the plasma jet changes drastically when the jet passes from a tube of higher permittivity to one of lower permittivity, resulting in an increase in jet length, ionization rate and electric field, as well as a change in the distribution of space charges and discharge states. The radius of the dielectric tube has a great influence on the ring-shaped or solid bullet structure. These results can well explain the behavior of the plasma jet from the dielectric tube into the ambient air and the hollow bullet in experiments.

Piezoelectric Response of Ferroelectric Ceramics Under Mechanical Stress

Science.gov (United States)

2015-09-17

response of the bulk Barium Titanate-based dielectric in such capacitors has not yet been addressed for shocks above 3,000 g. Thus, the current research...3.15 Low Voltage Capacitor Dielectric Volume Sections . . . . . . . . . . . . . . . 81 3.16 Electrodes, Terminals and Boundary Condition Surfaces...Final Separation from the Flexing Board of 1812 Capacitor after 36-inch Drop . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 4.21 Dielectric

Self-Healing, High-Permittivity Silicone Dielectric Elastomer

DEFF Research Database (Denmark)

Madsen, Frederikke Bahrt; Yu, Liyun; Skov, Anne Ladegaard

2016-01-01

possesses high dielectric permittivity and consists of an interpenetrating polymer network of silicone elastomer and ionic silicone species that are cross-linked through proton exchange between amines and acids. The ionically cross-linked silicone provides self-healing properties after electrical breakdown...... or cuts made directly to the material due to the reassembly of the ionic bonds that are broken during damage. The dielectric elastomers presented in this paper pave the way to increased lifetimes and the ability of dielectric elastomers to survive millions of cycles in high-voltage conditions....

Dielectric behaviour of strontium tartrate single crystals

Indian Academy of Sciences (India)

Unknown

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

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

DEFF Research Database (Denmark)

Mortensen, Asger; Sigmund, Ole; Breinbjerg, Olav

2009-01-01

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

From surface to volume plasmons in hyperbolic metamaterials: General existence conditions for bulk high-k waves in metal-dielectric and graphene-dielectric multilayers

DEFF Research Database (Denmark)

Zhukovsky, Sergei; Andryieuski, Andrei; Sipe, John E.

2014-01-01

-dielectric and recently introduced graphene-dielectric stacks. We confirm that short-range surface plasmons in thin metal layers can give rise to hyperbolic metamaterial properties and demonstrate that long-range surface plasmons cannot. We also show that graphene-dielectric multilayers tend to support high- k waves...

Dielectric relaxation studies in super-cooled liquid and glassy phases of anti-cancerous alkaloid: Brucine

Science.gov (United States)

Afzal, Aboothahir; Shahin Thayyil, M.; Sulaiman, M. K.; Kulkarni, A. R.

2018-05-01

Brucine has good anti-tumor effects, on both liver cancer and breast cancer. It has bioavailability of 40.83%. Since the bioavailability of the drug is low, an alternative method to increase its bioavailability and solubility is by changing the drug into glassy form. We used Differential Scanning Calorimetry (DSC) for studying the glass forming ability of the drug. Brucine was found to be a very good glass former glass transition temperature 365 K. Based on the DSC analysis we have used broadband dielectric spectroscopy (BDS) for studying the drug in the super cooled and glassy state. BDS is an effective tool to probe the molecular dynamics in the super cooled and glassy state. Molecular mobility is found to be present even in the glassy state of this active pharmaceutical ingredient (API) which is responsible for the instability. Our aim is to study the factors responsible for instability of this API in amorphous form. Cooling curves for dielectric permittivity and dielectric loss revealed the presence of structural (α) and secondary relaxations (β and γ). Temperature dependence of relaxation time is fitted by Vogel-Fulcher-Tammann equation and found the values of activation energy of the α relaxation, fragility and glass transition temperature. Paluch's anti correlation is also verified, that the width of the α-loss peak at or near the glass transition temperature Tg is strongly anticorrelated with the polarity of the molecule. The larger the dielectric relaxation strength Δɛ (Tg) of the system, the narrower is the α-loss peak (higher value of βKWW).

Effects of N2O plasma treatment on perhydropolysilazane spin-on-dielectrics for inter-layer-dielectric applications

International Nuclear Information System (INIS)

Park, Kyoung-Seok; Ko, Pil-Seok; Kim, Sam-Dong

2014-01-01

Effects of the N 2 O plasma treatment (PT) on perhydropolysilazane spin-on-dielectric (PHPS SOD) were examined as potential inter-layer-dielectrics (ILDs) for sub-30 nm Si circuits. The spin-coated PHPS (18.5 wt.%) ILD layers converted at 650 °C were integrated with the 0.18 μm Si front-end-of-the line process. A modified contact pre-cleaning scheme using N 2 O PT produced more uniform and stable contact chain resistances from the SOD ILDs than the case of pre-cleaning only by buffered oxide etcher. Our analysis shows that this enhancement is due to the minimized carbon contamination on the PHPS side-wall surface densified by PT. - Highlights: • Perhydropolysilazane (PHPS) layer is evaluated as a Si interlayer dielectric. • Examine effects of the N 2 O plasma treatment (PT) on PHPS spin-on-dielectrics (SODs) • Significantly improved metal contact resistances are achieved using the N 2 O PT. • Contact resistance enhancement by PT is due to the minimized carbon contamination

Response of single polymers to localized step strains

NARCIS (Netherlands)

Panja, D.

2009-01-01

In this paper, the response of single three-dimensional phantom and self-avoiding polymers to localized step strains are studied for two cases in the absence of hydrodynamic interactions: (i) Polymers tethered at one end with the strain created at the point of tether, and (ii) free polymers with the

Dielectric function of semiconductor superlattice

International Nuclear Information System (INIS)

Qin Guoyi.

1990-08-01

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

Dielectric relaxations in non-metallic materials related to Y-Ba-Cu-O superconductors

Energy Technology Data Exchange (ETDEWEB)

Bennani, H.; Pilet, J.C. (Lab. Instrumentation, Rennes-1 Univ., 35 (France)); Guilloux-Viry, M.; Perrin, C.; Perrin, A.; Sergent, M. (Lab. de Chimie Minerale B, C.N.R.S., 35 - Rennes (France))

1990-10-15

In relation with high Tc superconducting material studies, dielectric measurements have been carried out, in the frequency range 10 Hz - 100 kHz, on two powdered compounds belonging to the Y-Ba-Cu-O system. The non-metallic tetragonal phases YBa{sub 2}Cu{sub 3}O{sub 6+x} exhibit dielectric relaxations: for the studied samples (x<0.4) the activation energy U is observed in the range 0.5local dissymmetries induced by oxygen vacancies in the Cu-O chains. The insulating green phase Y{sub 2}BaCuO{sub 5} has a lower activation energy U {approx equal} 0.4 eV and an entropy factor A {approx equal} 10{sup 10} Hz. A second dielectric relaxation has been detected at higher temperature, near 400 K. Additional measurements to 77 K at 1 MHz give a value of dielectric constant {epsilon}'=3 and a low loss factor tg{delta}=10{sup -3}: this latter value is comparable to the one of lanthanum gallate recently proposed as a substrate for high frequency uses. This result enhances the previously reported potential interest of this material as substrate or buffer layer for preparation of superconducting thin films for high frequency applications. (orig.).

Dielectric elastomer actuators used for pneumatic valve technology

International Nuclear Information System (INIS)

Giousouf, Metin; Kovacs, Gabor

2013-01-01

Dielectric elastomer actuators have been investigated for applications in the field of pneumatic automation technology. We have developed different valve designs with stacked dielectric elastomer actuators and with integrated high voltage converters. The actuators were made using VHB-4910 material and a stacker machine for automated fabrication of the cylindrical actuators. Typical characteristics of pneumatic valves such as flow rate, power consumption and dynamic behaviour are presented. For valve construction the force and stroke parameters of the dielectric elastomer actuator have been measured. Further, benefits for valve applications using dielectric elastomers are shown as well as their potential operational area. Finally, challenges are discussed that are relevant for the use of elastomer actuators in valves for industrial applications. (paper)

Dielectric relaxation studies of dilute solutions of amides

Energy Technology Data Exchange (ETDEWEB)

Malathi, M.; Sabesan, R.; Krishnan, S

2003-11-15

The dielectric constants and dielectric losses of formamide, acetamide, N-methyl acetamide, acetanilide and N,N-dimethyl acetamide in dilute solutions of 1,4-dioxan/benzene have been measured at 308 K using 9.37 GHz, dielectric relaxation set up. The relaxation time for the over all rotation {tau}{sub (1)} and that for the group rotation {tau}{sub (2)} of (the molecules were determined using Higasi's method. The activation energies for the processes of dielectric relaxation and viscous flow were determined by using Eyring's rate theory. From relaxation time behaviour of amides in non-polar solvent, solute-solvent and solute-solute type of molecular association is proposed.

Temperature dependence of the dielectric properties of rubber wood

Science.gov (United States)

Mohammed Firoz Kabir; Wan M. Daud; Kaida B. Khalid; Haji A.A. Sidek

2001-01-01

The effect of temperature on the dielectric properties of rubber wood was investigated in three anisotropic directions—longitudinal, radial, and tangential, and at different measurement frequencies. Low frequency measurements were conducted with a dielectric spectrometer, and high frequencies used microwave applied with open-ended coaxial probe sensors. Dielectric...

Structure and phase formation behavior and dielectric and magnetic properties of lead iron tantalate-lead zirconate titanate multiferroic ceramics

International Nuclear Information System (INIS)

Wongmaneerung, R.; Tipakontitikul, R.; Jantaratana, P.; Bootchanont, A.; Jutimoosik, J.; Yimnirun, R.; Ananta, S.

2016-01-01

Highlights: • The multiferroic ceramics consisted of PFT and PZT. • Crystal structure changed from cubic to mixedcubic and tetragonal with increasing PZT content. • Dielectric showed the samples underwent a typical relaxor ferroelectric behavior. • Magnetic properties showed very interesting behavior with square saturated magnetic hysteresis loops. - Abstract: Multiferroic (1 − x)Pb(Fe_0_._5Ta_0_._5)O_3–xPb(Zr_0_._5_3Ti_0_._4_7)O_3 (or PFT–PZT) ceramics were synthesized by solid-state reaction method. The crystal structure and phase formation of the ceramics were examined by X-ray diffraction (XRD). The local structure surrounding Fe and Ti absorbing atoms was investigated by synchrotron X-ray Absorption Near-Edge Structure (XANES) measurement. Dielectric properties were studied as a function of frequency and temperature using a LCR meter. A vibrating sample magnetometer (VSM) was used to determine the magnetic hysteresis loops. XRD study indicated that the crystal structure of the sample changed from pure cubic to mixed cubic and tetragonal with increasing PZT content. XANES measurements showed that the local structure surrounding Fe and Ti ions was similar. Dielectric study showed that the samples underwent a typical relaxor ferroelectric behavior while the magnetic properties showed very interesting behavior with square saturated magnetic hysteresis loops.

Impedance matching of pillbox-type RF windows and direct measurement of the ceramic relative dielectric constant

Energy Technology Data Exchange (ETDEWEB)

Ao, Hiroyuki, E-mail: hiroyuki.ao@j-parc.jp [Japan Atomic Energy Agency (JAEA), J-PARC Center, Accelerator Division, 2-4, Shirakara Shirane, Tokai, Naka, Ibaraki 319-1195 (Japan); Asano, Hiroyuki [Japan Atomic Energy Agency (JAEA), J-PARC Center, Accelerator Division, 2-4, Shirakara Shirane, Tokai, Naka, Ibaraki 319-1195 (Japan); Naito, Fujio [High Energy Accelerator Research Organization (KEK), 1-1, Oho, Tsukuba, Ibaraki 305-0801 (Japan); Ouchi, Nobuo; Tamura, Jun [Japan Atomic Energy Agency (JAEA), J-PARC Center, Accelerator Division, 2-4, Shirakara Shirane, Tokai, Naka, Ibaraki 319-1195 (Japan); Takata, Koji [High Energy Accelerator Research Organization (KEK), 1-1, Oho, Tsukuba, Ibaraki 305-0801 (Japan)

2014-02-11

Impedance matching of RF windows that minimizes the RF reflection is necessary to prevent localized standing waves between an RF window and a cavity, which may cause thermal and/or multipactoring issues. It has been observed that the impedance matching condition of the pillbox-type RF window, checked by voltage standing wave ratio (VSWR) measurement, depends on the manufacturing lot of the window ceramic disk made of 95% purity Al{sub 2}O{sub 3}. The present report proposes new procedures for impedance matching as follows: (i) The relative dielectric constant of the ceramic window is directly measured using the resonant frequency of a cavity made by temporarily combining the pillbox part of the RF window and two short-circuiting plates. (ii) The dimensions of the pillbox section including the ceramic disk are fixed on the basis of the measured relative dielectric constant. To confirm this procedure, three RF windows were fabricated using the same type of ceramic material, and successful impedance matching of these windows was performed (VSWR<1.05). The measured results also suggest that the relative dielectric constant increases linearly with increasing density and that the impedance matching condition is mainly affected by variations of the relative dielectric constant due to shrinkage of the alumina during sintering. -- Highlights: • We measured the relative dielectric constant of an RF window ceramic directly. • We used the circular TE011-mode frequency of the pillbox part of an RF window itself. • The dimensions of the pillbox part were fixed on the basis of the measurement result. • Three RF windows were fabricated, and VSWR <1.05 for these windows was performed. • The relative dielectric constant increases linearly with increasing ceramic density.

Impedance matching of pillbox-type RF windows and direct measurement of the ceramic relative dielectric constant

International Nuclear Information System (INIS)

Ao, Hiroyuki; Asano, Hiroyuki; Naito, Fujio; Ouchi, Nobuo; Tamura, Jun; Takata, Koji

2014-01-01

Impedance matching of RF windows that minimizes the RF reflection is necessary to prevent localized standing waves between an RF window and a cavity, which may cause thermal and/or multipactoring issues. It has been observed that the impedance matching condition of the pillbox-type RF window, checked by voltage standing wave ratio (VSWR) measurement, depends on the manufacturing lot of the window ceramic disk made of 95% purity Al 2 O 3 . The present report proposes new procedures for impedance matching as follows: (i) The relative dielectric constant of the ceramic window is directly measured using the resonant frequency of a cavity made by temporarily combining the pillbox part of the RF window and two short-circuiting plates. (ii) The dimensions of the pillbox section including the ceramic disk are fixed on the basis of the measured relative dielectric constant. To confirm this procedure, three RF windows were fabricated using the same type of ceramic material, and successful impedance matching of these windows was performed (VSWR<1.05). The measured results also suggest that the relative dielectric constant increases linearly with increasing density and that the impedance matching condition is mainly affected by variations of the relative dielectric constant due to shrinkage of the alumina during sintering. -- Highlights: • We measured the relative dielectric constant of an RF window ceramic directly. • We used the circular TE011-mode frequency of the pillbox part of an RF window itself. • The dimensions of the pillbox part were fixed on the basis of the measurement result. • Three RF windows were fabricated, and VSWR <1.05 for these windows was performed. • The relative dielectric constant increases linearly with increasing ceramic density

Preparation and Characterization of Pure Organic Dielectric Composites for Capacitors

Directory of Open Access Journals (Sweden)

Mao Xin

2018-01-01

Full Text Available This work reports the excellent dielectric composites were prepared from polyimide (PI and poly(vinylidene fluoride (PVDF via solution blending and thermal imidization or chemical imidization. The dielectric and thermal properties of the composites were studied. Results indicated that the dielectric properties of the composites synthesized by these two methods were enhanced through the introduction of PVDF, and the composites exhibited excellent thermal stability. Compared to the thermal imidization, the composites prepared by chemical imidization exhibited superior dielectric properties. This study demonstrated that the PI/PVDF composites were potential dielectric materials in the field of electronics.

Analysis of transmittance properties in 1D hybrid dielectric photonic crystal containing superconducting thin films

Science.gov (United States)

Soltani, Osswa; Zaghdoudi, Jihene; Kanzari, Mounir

2018-06-01

By means of two fluid model and transfer matrix method (TMM), we investigate theoretically the transmittance properties of a defective hybrid dielectric-dielectric photonic crystal that contains a superconducting material as a defect layer. The considered hybrid photonic structure is: H(LH) 7(HLSLH) P H(LH) 7 , where H is the high refractive index dielectric, L is the low refractive index dielectric, S is the superconducting material and P is the repetitive number. The results show that the variation of the number and the positions of the transmissions modes depend strongly on the repetitive number P, the temperature T and the thickness of the layer S. An improvement of the spectral response is obtained with the exponential gradation of layer thicknesses dj =d0 + βejα , where d0 is the initial thickness of the layer j, α and β are two particular constants for each material. In addition, the effect of the incident angle for both transverse electric (TE) and transverse magnetic (TM) polarizations on the transmittance spectrum is discussed. As a result, we propose a tunable narrow stop-band polychromatic filter that covers the visible wavelength.

Perceived Facilitators and Barriers to Local Health Department Workers' Participation in Infectious Disease Emergency Responses.

Science.gov (United States)

Rutkow, Lainie; Paul, Amy; Taylor, Holly A; Barnett, Daniel J

Local health departments play a key role in emergency preparedness and respond to a wide range of threats including infectious diseases such as seasonal influenza, tuberculosis, H1N1, Ebola virus disease, and Zika virus disease. To successfully respond to an infectious disease outbreak, local health departments depend upon the participation of their workforce; yet, studies indicate that sizable numbers of workers would not participate in such a response. The reasons why local health department workers participate, or fail to participate, in infectious disease responses are not well understood. To understand why local health department workers are willing, or not willing, to report to work during an infectious disease response. From April 2015 to January 2016, we conducted 28 semistructured interviews with local health department directors, preparedness staff, and nonpreparedness staff. Interviews were conducted with individuals throughout the United States. We interviewed 28 individuals across 3 groups: local health department directors (n = 8), preparedness staff (n = 10), and nonpreparedness staff (n = 10). Individuals' descriptions of why local health department workers are willing, or not willing, to report to work during an infectious disease response. Factors that facilitate willingness to respond to an infectious disease emergency included availability of vaccines and personal protective equipment; flexible work schedule and childcare arrangements; information sharing via local health department trainings; and perceived commitments to one's job and community. Factors that hinder willingness to respond to an infectious disease emergency included potential disease exposure for oneself and one's family; logistical considerations for care of children, the elderly, and pets; and perceptions about one's role during an infectious disease response. Our findings highlight opportunities for local health departments to revisit their internal policies and engage in

High temperature polymer film dielectrics for aerospace power conditioning capacitor applications

Energy Technology Data Exchange (ETDEWEB)

Venkat, Narayanan, E-mail: venkats3@gmail.co [University of Dayton Research Institute (UDRI), Dayton, OH 45469 (United States); Dang, Thuy D. [Air Force Research Laboratory-Nanostructured and Biological Materials Branch (AFRL/RXBN) (United States); Bai Zongwu; McNier, Victor K. [University of Dayton Research Institute (UDRI), Dayton, OH 45469 (United States); DeCerbo, Jennifer N. [Air Force Research Laboratory-Electrical Technology Branch (AFRL/RZPE), Wright-Patterson Air Force Base, OH 45433 (United States); Tsao, B.-H. [University of Dayton Research Institute (UDRI), Dayton, OH 45469 (United States); Stricker, Jeffery T. [Air Force Research Laboratory-Electrical Technology Branch (AFRL/RZPE), Wright-Patterson Air Force Base, OH 45433 (United States)

2010-04-15

Polymer dielectrics are the preferred materials of choice for capacitive energy-storage applications because of their potential for high dielectric breakdown strengths, low dissipation factors and good dielectric stability over a wide range of frequencies and temperatures, despite having inherently lower dielectric constants relative to ceramic dielectrics. They are also amenable to large area processing into films at a relatively lower cost. Air Force currently has a strong need for the development of compact capacitors which are thermally robust for operation in a variety of aerospace power conditioning applications. While such applications typically use polycarbonate (PC) dielectric films in wound capacitors for operation from -55 deg. C to 125 deg. C, future power electronic systems would require the use of polymer dielectrics that can reliably operate up to elevated temperatures in the range of 250-350 deg. C. The focus of this research is the generation and dielectric evaluation of metallized, thin free-standing films derived from high temperature polymer structures such as fluorinated polybenzoxazoles, post-functionalized fluorinated polyimides and fluorenyl polyesters incorporating diamond-like hydrocarbon units. The discussion is centered mainly on variable temperature dielectric measurements of film capacitance and dissipation factor and the effects of thermal cycling, up to a maximum temperature of 350 deg. C, on film dielectric performance. Initial studies clearly point to the dielectric stability of these films for high temperature power conditioning applications, as indicated by their relatively low temperature coefficient of capacitance (TCC) (approx2%) over the entire range of temperatures. Some of the films were also found to exhibit good dielectric breakdown strengths (up to 470 V/mum) and a film dissipation factor of the order of <0.003 (0.3%) at the frequency of interest (10 kHz) for the intended applications. The measured relative dielectric

Plasma polymerized high energy density dielectric films for capacitors

Science.gov (United States)

Yamagishi, F. G.

1983-01-01

High energy density polymeric dielectric films were prepared by plasma polymerization of a variety of gaseous monomers. This technique gives thin, reproducible, pinhole free, conformable, adherent, and insoluble coatings and overcomes the processing problems found in the preparation of thin films with bulk polymers. Thus, devices are prepared completely in a vacuum environment. The plasma polymerized films prepared all showed dielectric strengths of greater than 1000 kV/cm and in some cases values of greater than 4000 kV/cm were observed. The dielectric loss of all films was generally less than 1% at frequencies below 10 kHz, but this value increased at higher frequencies. All films were self healing. The dielectric strength was a function of the polymerization technique, whereas the dielectric constant varied with the structure of the starting material. Because of the thin films used (thickness in the submicron range) surface smoothness of the metal electrodes was found to be critical in obtaining high dielectric strengths. High dielectric strength graft copolymers were also prepared. Plasma polymerized ethane was found to be thermally stable up to 150 C in the presence of air and 250 C in the absence of air. No glass transitions were observed for this material.

Radiotherapy in desmoid tumors. Treatment response, local control, and analysis of local failures

Energy Technology Data Exchange (ETDEWEB)

Santti, Kirsi; Beule, Annette; Tuomikoski, Laura; Jaeaeskelaeinen, Anna-Stina; Saarilahti, Kauko; Tarkkanen, Maija; Blomqvist, Carl [Helsinki University Hospital and University of Helsinki, Comprehensive Cancer Center, Helsinki (Finland); Roenty, Mikko [HUSLAB and University of Helsinki, Department of Pathology, Helsinki (Finland); Ihalainen, Hanna [Helsinki University Hospital and University of Helsinki, Department of Plastic Surgery, Helsinki (Finland)

2017-04-15

Desmoid tumors (aggressive fibromatosis) are rare soft tissue tumors which frequently recur after surgery. Desmoid tumors arise from musculoaponeurotic tissue in the extremities, head and neck, abdominal wall, or intra-abdominally. Our aim was to examine the outcome of radiotherapy of desmoid tumors in a single institution series. We evaluated 41 patients with desmoid tumors treated with 49 radiotherapies between 1987 and 2012. Radiologic images for response evaluation were reassessed and responses to treatment registered according to RECIST criteria 1.1. For patients with local failures radiation dose distribution was determined in each local failure volume using image co-registration. Recurrences were classified as in-target, marginal, or out-of-target. Prognostic factors for radiotherapy treatment failure were evaluated. Radiotherapy doses varied from 20-63 Gy (median 50 Gy) with a median fraction size of 2 Gy. The objective response rate to definitive radiotherapy was 55% (12/22 patients). Median time to response was 14 months. A statistically significant dose-response relation for definitive and postoperative radiotherapy was observed both in univariate (p-value 0.002) and in multivariate analysis (p-value 0.02) adjusted for potential confounding factors. Surgery before radiotherapy or surgical margin had no significant effect on time to progression. Nine of 11 (82%) local failures were classified as marginal and two of 11 (18%) in-target. None of the recurrences occurred totally out-of-target. Radiotherapy is a valuable option for treating desmoid tumors. Radiotherapy dose appears to be significantly associated to local control. (orig.) [German] Desmoide (aggressive Fibromatosen) sind seltene Weichteiltumore der muskulaeren Membranen von Kopf, Hals, Extremitaeten und Bauchwand. Ziel war es, die Wirksamkeit der Strahlentherapie bei aggressiver Fibromatose an einer einzelnen Klinik zu untersuchen. Ausgewertet wurden 41 Patienten mit aggressiver Fibromatose, die

Local and linear chemical reactivity response functions at finite temperature in density functional theory

International Nuclear Information System (INIS)

Franco-Pérez, Marco; Ayers, Paul W.; Gázquez, José L.; Vela, Alberto

2015-01-01

We explore the local and nonlocal response functions of the grand canonical potential density functional at nonzero temperature. In analogy to the zero-temperature treatment, local (e.g., the average electron density and the local softness) and nonlocal (e.g., the softness kernel) intrinsic response functions are defined as partial derivatives of the grand canonical potential with respect to its thermodynamic variables (i.e., the chemical potential of the electron reservoir and the external potential generated by the atomic nuclei). To define the local and nonlocal response functions of the electron density (e.g., the Fukui function, the linear density response function, and the dual descriptor), we differentiate with respect to the average electron number and the external potential. The well-known mathematical relationships between the intrinsic response functions and the electron-density responses are generalized to nonzero temperature, and we prove that in the zero-temperature limit, our results recover well-known identities from the density functional theory of chemical reactivity. Specific working equations and numerical results are provided for the 3-state ensemble model

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

Science.gov (United States)

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

2013-12-01

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

Dielectric behaviour of erbium substituted Mn–Zn ferrites

Indian Academy of Sciences (India)

Unknown

Abstract. Dielectric properties such as dielectric constant (ε′) and dielectric loss tangent (tan δ) of mixed. Mn–Zn–Er ferrites having the compositional formula Mn0⋅58Zn0⋅37Fe2⋅05–xErxO4 (where x = 0⋅2, 0⋅4, 0⋅6, 0⋅8 and. 1⋅0) were measured at room temperature in the frequency range 1–13 MHz using a HP ...

Three-dimensional periodic dielectric structures having photonic Dirac points

Science.gov (United States)

Bravo-Abad, Jorge; Joannopoulos, John D.; Soljacic, Marin

2015-06-02

The dielectric, three-dimensional photonic materials disclosed herein feature Dirac-like dispersion in quasi-two-dimensional systems. Embodiments include a face-centered cubic (fcc) structure formed by alternating layers of dielectric rods and dielectric slabs patterned with holes on respective triangular lattices. This fcc structure also includes a defect layer, which may comprise either dielectric rods or a dielectric slab with patterned with holes. This defect layer introduces Dirac cone dispersion into the fcc structure's photonic band structure. Examples of these fcc structures enable enhancement of the spontaneous emission coupling efficiency (the .beta.-factor) over large areas, contrary to the conventional wisdom that the .beta.-factor degrades as the system's size increases. These results enable large-area, low-threshold lasers; single-photon sources; quantum information processing devices; and energy harvesting systems.

PLZT capacitor and method to increase the dielectric constant

Science.gov (United States)

Taylor, Ralph S.; Fairchild, Manuel Ray; Balachjandran, Uthamalingam; Lee, Tae H.

2017-12-12

A ceramic-capacitor includes a first electrically-conductive-layer, a second electrically-conductive-layer arranged proximate to the first electrically-conductive-layer, and a dielectric-layer interposed between the first electrically-conductive-layer and the second electrically-conductive-layer. The dielectric-layer is formed of a lead-lanthanum-zirconium-titanate material (PLZT), wherein the PLZT is characterized by a dielectric-constant greater than 125, when measured at 25 degrees Celsius and zero Volts bias, and an excitation frequency of ten-thousand Hertz (10 kHz). A method for increasing a dielectric constant of the lead-lanthanum-zirconium-titanate material (PLZT) includes the steps of depositing PLZT to form a dielectric-layer of a ceramic-capacitor, and heating the ceramic-capacitor to a temperature not greater than 300.degree. C.

Three-dimensional periodic dielectric structures having photonic Dirac points

Energy Technology Data Exchange (ETDEWEB)

Bravo-Abad, Jorge; Joannopoulos, John D.; Soljacic, Marin

2015-06-02

The dielectric, three-dimensional photonic materials disclosed herein feature Dirac-like dispersion in quasi-two-dimensional systems. Embodiments include a face-centered cubic (fcc) structure formed by alternating layers of dielectric rods and dielectric slabs patterned with holes on respective triangular lattices. This fcc structure also includes a defect layer, which may comprise either dielectric rods or a dielectric slab with patterned with holes. This defect layer introduces Dirac cone dispersion into the fcc structure's photonic band structure. Examples of these fcc structures enable enhancement of the spontaneous emission coupling efficiency (the .beta.-factor) over large areas, contrary to the conventional wisdom that the .beta.-factor degrades as the system's size increases. These results enable large-area, low-threshold lasers; single-photon sources; quantum information processing devices; and energy harvesting systems.

Experimental investigation on local mechanical response of superelastic NiTi shape memory alloy

International Nuclear Information System (INIS)

Xiao, Yao; Zeng, Pan; Lei, Liping

2016-01-01

In this paper, primary attention is paid to the local mechanical response of NiTi shape memory alloy (SMA) under uniaxial tension. With the help of in situ digital image correlation, sets of experiments are conducted to measure the local strain field at various thermomechanical conditions. Two types of mechanical responses of NiTi SMA are identified. The residual strain localization phenomena are observed, which can be attributed to the localized phase transformation (PT) and we affirm that most of the irreversibility is accumulated simultaneously during PT. It is found that temperature and PT play important roles in inducing delocalization of the reverse transformation. We conclude that forward transformation has more influence on the transition of mechanical response in NiTi SMA than reverse transformation in terms of the critical transition temperature for inducing delocalized reverse transformation. (technical note)

Effect of nanocomposite gate-dielectric properties on pentacene microstructure and field-effect transistor characteristics.

Science.gov (United States)

Lee, Wen-Hsi; Wang, Chun-Chieh

2010-02-01

In this study, the effect of surface energy and roughness of the nanocomposite gate dielectric on pentacene morphology and electrical properties of pentacene OTFT are reported. Nanoparticles TiO2 were added in the polyimide matrix to form a nanocomposite which has a significantly different surface characteristic from polyimide, leading to a discrepancy in the structural properties of pentacene growth. A growth mode of pentacene deposited on the nanocomposite is proposed to explain successfully the effect of surface properties of nanocomposite gate dielectric such as surface energy and roughness on the pentacene morphology and electrical properties of OTFT. To obtain the lower surface energy and smoother surface of nanocomposite gate dielectric that is responsible for the desired crystalline, microstructure of pentacene and electrical properties of device, a bottom contact OTFT-pentacene deposited on the double-layer nanocomposite gate dielectric consisting of top smoothing layer of the neat polyimide and bottom layer of (PI+ nano-TiO2 particles) nanocomposite has been successfully demonstrated to exhibit very promising performance including high current on to off ratio of about 6 x 10(5), threshold voltage of -10 V and moderately high filed mobility of 0.15 cm2V(-1)s(-1).

Conductivity and dielectric behaviour of indium substituted zinc ferrites prepared by coprecipitation method

International Nuclear Information System (INIS)

Cvejić, Željka; Rakić, Srđan; Jankov, Stevan; Skuban, Sonja; Rapajić, Sanja; Srdić, Vladimir V

2015-01-01

This paper presents the results concerning dielectric behavior and conductivity of the nanosized Zn 1−x In x Fe 2 O 4 powders (x = 0, 0.15, 0.2, and 0.3), obtained by coprecipitation method. The frequency dependence of dielectric permittivity and conductivity of the samples is determined in the frequency range of 1–10 5 Hz, at temperatures from 300–350 K, while the temperature dependence of conductivity was recorded at 100 Hz, 10 kHz and 100 kHz. The ac conductivity was found to follow universal dielectric response, which is typical for charge transport by hopping or tunneling processes. Analyzing the variation of the parameter n (as a measure of the degree of correlation between conductivity and frequency), with the temperatures we discuss the possible conduction mechanism in investigated samples. Qualitatively, non-overlapping small polarons (NSPT) are usually associated with increase in n with increasing temperature, while correlated barrier hopping (CBH) shows a decrease in n with increasing T. (paper)

Slots in dielectric image line as mode launchers and circuit elements

Science.gov (United States)

Solbach, K.

1981-01-01

A planar resonator model is used to investigate slots in the ground plane of dielectric image lines. An equivalent circuit representation of the slot discontinuity is obtained, and the launching efficiency of the slot as a mode launcher is analyzed. Slots are also shown to be useful in the realization of dielectric image line array antennas. It is found that the slot discontinuity can be shown as a T-junction of the dielectric image line and a metal waveguide. The launching efficiency is found to increase with the dielectric constant of the dielectric image line, exhibiting a maximum value for guides whose height is slightly less than half a wavelength in the dielectric medium. The measured launching efficiencies of low permittivity dielectric image lines are found to be in good agreement with calculated values

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

Science.gov (United States)

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

2014-03-01

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

RF cavity using liquid dielectric for tuning and cooling

Science.gov (United States)

Popovic, Milorad [Warrenville, IL; Johnson, Rolland P [Newport News, VA

2012-04-17

A system for accelerating particles includes an RF cavity that contains a ferrite core and a liquid dielectric. Characteristics of the ferrite core and the liquid dielectric, among other factors, determine the resonant frequency of the RF cavity. The liquid dielectric is circulated to cool the ferrite core during the operation of the system.

Dielectric and photo-dielectric properties of TlGaSeS crystals

Indian Academy of Sciences (India)

Administrator

cDepartment of Physics, Middle East Technical University, 06800 Ankara, Turkey. MS received ... The crystals are observed to exhibit a dark high frequency effective dielectric constant value of ~ 10\\65 x ... communication systems. Keywords.

Interfacial Cation-Defect Charge Dipoles in Stacked TiO2/Al2O3 Gate Dielectrics.

Science.gov (United States)

Zhang, Liangliang; Janotti, Anderson; Meng, Andrew C; Tang, Kechao; Van de Walle, Chris G; McIntyre, Paul C

2018-02-14

Layered atomic-layer-deposited and forming-gas-annealed TiO 2 /Al 2 O 3 dielectric stacks, with the Al 2 O 3 layer interposed between the TiO 2 and a p-type germanium substrate, are found to exhibit a significant interface charge dipole that causes a ∼-0.2 V shift of the flat-band voltage and suppresses the leakage current density for gate injection of electrons. These effects can be eliminated by the formation of a trilayer dielectric stack, consistent with the cancellation of one TiO 2 /Al 2 O 3 interface dipole by the addition of another dipole of opposite sign. Density functional theory calculations indicate that the observed interface-dependent properties of TiO 2 /Al 2 O 3 dielectric stacks are consistent in sign and magnitude with the predicted behavior of Al Ti and Ti Al point-defect dipoles produced by local intermixing of the Al 2 O 3 /TiO 2 layers across the interface. Evidence for such intermixing is found in both electrical and physical characterization of the gate stacks.

Porous (Ba,SrTiO3 ceramics for tailoring dielectric and tunability properties: Modelling and experiment

Directory of Open Access Journals (Sweden)

Roxana E. Stanculescu

2017-12-01

Full Text Available 3D Finite Element Method simulations were employed in order to describe tunability properties in anisotropic porous paraelectric structures. The simulations predicted that properties of a ceramic can be tailored by using various levels of porosity. Porous Ba0.6Sr0.4TiO3 (BST ceramics have been studied in order to investigate the influence of porosity on their functional properties. The BST ceramics with various porosity levels have been obtained by solid-state reaction. Lamellar graphite in different concentration of 10, 20 and 35 vol.% was added as sacrificial pore forming agent. The structural, microstructural, dielectric and tunability properties were investigated. By comparison with dense BST ceramic, porous samples present a fracture mode transformation from intragranular to an intergranular fracture and a decrease of grain size. Lower dielectric constants, low dielectric losses, but higher values of tunability than in the dense material were obtained in the porous BST structures as a result of local field inhomogeneity generated by the presence of air pores-ceramic interfaces.

Dielectric Properties of Cd1-xZnxSe Thin Film Semiconductors

International Nuclear Information System (INIS)

Wahab, L.A.; Farrag, A.A.; Zayed, H.A.

2012-01-01

Cd 1-x Zn x Se (x=0, 0.5 and 1) thin films of thickness 300 nm have been deposited on highly cleaned glass substrates (Soda-lime glass) by thermal evaporation technique under pressure 10-5 Torr. The crystal structure, lattice parameters and grain size were determined from X-ray diffraction patterns of these films. The dielectric response and ac conductivity of the films are investigated in the frequency range from 80 Hz to 5 MHz and temperature range from 300 K to 420 K. AC conductivity increases linearly with the frequency according to the power relation σ a c (ψ)=A (ψ) s . The dielectric constant and loss show low values at high frequencies. The relaxation time t, resistance R and capacitance C were calculated from Nyquist diagram. The behavior can be modeled by an equivalent parallel RC circuit.

Energy storage in ceramic dielectrics

International Nuclear Information System (INIS)

Love, G.R.

1990-01-01

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

Electrostatic field in inhomogeneous dielectric media. I. Indirect boundary element method

International Nuclear Information System (INIS)

Goel, N.S.; Gang, F.; Ko, Z.

1995-01-01

A computationally fast method is presented for calculating electrostatic field in arbitrary inhomogeneous dielectric media with open boundary condition. The method involves dividing the whole space into cubical cells and then finding effective dielectric parameters for interfacial cells consisting of several dielectrics. The electrostatic problem is then solved using either the indirect boundary element method described in this paper or the so-called volume element method described in the companion paper. Both methods are tested for accuracy by comparing the numerically calculated electrostatic fields against those analytically obtained for a dielectric sphere and dielectric ellipsoid in a uniform field and for a dielectric sphere in a point charge field

A Flexible Capacitive Sensor with Encapsulated Liquids as Dielectrics

Directory of Open Access Journals (Sweden)

Yasunari Hotta

2012-03-01

Full Text Available Flexible and high-sensitive capacitive sensors are demanded to detect pressure distribution and/or tactile information on a curved surface, hence, wide varieties of polymer-based flexible MEMS sensors have been developed. High-sensitivity may be achieved by increasing the capacitance of the sensor using solid dielectric material while it deteriorates the flexibility. Using air as the dielectric, to maintain the flexibility, sacrifices the sensor sensitivity. In this paper, we demonstrate flexible and highly sensitive capacitive sensor arrays that encapsulate highly dielectric liquids as the dielectric. Deionized water and glycerin, which have relative dielectric constants of approximately 80 and 47, respectively, could increase the capacitance of the sensor when used as the dielectric while maintaining flexibility of the sensor with electrodes patterned on flexible polymer substrates. A reservoir of liquids between the electrodes was designed to have a leak path, which allows the sensor to deform despite of the incompressibility of the encapsulated liquids. The proposed sensor was microfabricated and demonstrated successfully to have a five times greater sensitivity than sensors that use air as the dielectric.

Vegetable oil based liquid nanocomposite dielectric

Directory of Open Access Journals (Sweden)

Leon Chetty

2013-01-01

Full Text Available Physically smaller dielectric materials would improve the optimisation of space for power systems. Development of nanotechnology provides an effective way to improve the performances of insulating oils used in power system applications. In this research study, we focused on the development of nanomodified vegetable oils to be used in power transformers. Higher conduction currents were observed in virgin linseed oil than in virgin castor oil. However, for both virgin linseed and virgin castor oil, the DC conduction current increased approximately linearly with the applied DC voltage. In nanomodified linseed oil, the characteristic curve showed two distinct regions: a linear region (at lower applied voltage and a saturation region (at slightly higher voltage. Conversely, in nanomodified castor oil, the characteristic curve showed three distinct regions: a linear region (at lower applied voltage, a saturation region (at intermediate applied voltage and an exponential growth region (at higher applied voltage. The nanomodified linseed oil exhibited a better dielectric performance than the nanomodified castor oil. Overall, the addition of nanodielectrics to vegetable oils decreased the dielectric performance of the vegetable oils. The results of this study contribute to the understanding of the pre-breakdown phenomenon in liquid nanocomposite dielectrics.

Pursuing Polymer Dielectric Interfacial Effect in Organic Transistors for Photosensing Performance Optimization.

Science.gov (United States)

Wu, Xiaohan; Chu, Yingli; Liu, Rui; Katz, Howard E; Huang, Jia

2017-12-01

Polymer dielectrics in organic field-effect transistors (OFETs) are essential to provide the devices with overall flexibility, stretchability, and printability and simultaneously introduce charge interaction on the interface with organic semiconductors (OSCs). The interfacial effect between various polymer dielectrics and OSCs significantly and intricately influences device performance. However, understanding of this effect is limited because the interface is buried and the interfacial charge interaction is difficult to stimulate and characterize. Here, this challenge is overcome by utilizing illumination to stimulate the interfacial effect in various OFETs and to characterize the responses of the effect by measuring photoinduced changes of the OFETs performances. This systemic investigation reveals the mechanism of the intricate interfacial effect in detail, and mathematically explains how the photosensitive OFETs characteristics are determined by parameters including polar group of the polymer dielectric and the OSC side chain. By utilizing this mechanism, performance of organic electronics can be precisely controlled and optimized. OFETs with strong interfacial effect can also show a signal additivity caused by repeated light pulses, which is applicable for photostimulated synapse emulator. Therefore, this work enlightens a detailed understanding on the interface effect and provides novel strategies for optimizing OFET photosensory performances.

Effect of deformation and dielectric filling on electromagnetic ...

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

great significance in the development of microwave communication networks and ... media. Rectangular dielectric waveguide structures are analysed by Bierwirth ..... Schweig E, Bridges W B 1984 Computer analysis of dielectric waveguide: A ...

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

Indian Academy of Sciences (India)

Unknown

2001-10-09

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

7th International Symposium on Gaseous Dielectrics

CERN Document Server

James, David

1994-01-01

The Seventh International Symposium on Gaseous Dielectrics was held in Knoxville, Tennessee, U. S. A. , on April 24-28, 1994. The symposium continued the interdisciplinary character and comprehensive approach of the preceding six symposia. Gaseous DielecIries VII is a detailed record of the symposium proceedings. It covers recent advances and developments in a wide range of basic, applied and industrial areas of gaseous dielectrics. It is hoped that Gaseous DielecIries VII will aid future research and development in, and encourage wider industrial use of, gaseous dielectrics. The Organizing Committee of the Seventh International Symposium on Gaseous Dielectrics consisted of G. Addis (U. S. A. ), L. G. Christophorou (U. S. A. ), F. Y. Chu (Canada), A. H. Cookson (U. S. A. ), O. Farish (U. K. ), I. Gallimberti (Italy) , A. Garscadden (U. S. A. ), D. R. James (U. S. A. ), E. Marode (France), T. Nitta (Japan), W. Pfeiffer (Germany), Y. Qiu (China), I. Sauers (U. S. A. ), R. J. Van Brunt (U. S. A. ), and W. Zaengl...

Dielectric relaxation in AgI doped silver selenomolybdate glasses

Science.gov (United States)

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

2016-05-01

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

Method to characterize dielectric properties of powdery substances

Science.gov (United States)

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

2013-07-01

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