Nonlinear Dielectric Response of Water Treed XLPE Cable Insulation

Energy Technology Data Exchange (ETDEWEB)

Hvidsten, Sverre

1999-07-01

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

Infrared gas phase study on plasma-polymer interactions in high-current diffuse dielectric barrier discharge

NARCIS (Netherlands)

Liu, Y.; Welzel, S.; Starostin, S. A.; van de Sanden, M. C. M.; Engeln, R.; de Vries, H. W.

2017-01-01

A roll-to-roll high-current diffuse dielectric barrier discharge at atmospheric pressure was operated in air and Ar/N2/O2 gas mixtures. The exhaust gas from the discharge was studied using a high-resolution Fourier-transform infrared spectrometer in the range from 3000 to 750?cm-1 to unravel the

Defects in codoped NiO with gigantic dielectric response

Science.gov (United States)

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

2009-06-01

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

Actuation response of polyacrylate dielectric elastomers

DEFF Research Database (Denmark)

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

2001-01-01

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

Structure refinement, far infrared spectroscopy, and dielectric characterization of (1-x)La(Mg1/2Ti1/2)O3-xLa2/3TiO3 solid solutions

Science.gov (United States)

Salak, Andrei N.; Khalyavin, Dmitry D.; Ferreira, Victor M.; Ribeiro, José L.; Vieira, Luís G.

2006-05-01

Dielectric properties of (1-x)La(Mg1/2Ti1/2)O3-xLa2/3TiO3 [(1-x)LMT-xLT] ceramics (0infrared (FIR) frequency ranges. The crystal structure sequence in (1-x)LMT-xLT reported by different authors has been analyzed and revised. FIR spectroscopy was used to characterize the lattice contribution to the dielectric response at microwave frequencies. The complex dielectric function was evaluated from the reflectivity data and extrapolated down to a gigahertz range. Compositional variations of the fundamental microwave dielectric parameters estimated by different methods are compared and discussed. The dependence of the quality factor on the composition in LMT-LT is interpreted in terms of the reduction of spatial phonon correlations originated from the increasing amount of La vacancies. This approach could account for the compositional behavior of the dielectric loss commonly observed in a number of microwave mixed systems.

Dielectric constant and low-frequency infrared spectra for liquid water and ice Ih within the E3B model

Energy Technology Data Exchange (ETDEWEB)

Shi, L.; Ni, Y.; Drews, S. E. P.; Skinner, J. L. [Theoretical Chemistry Institute and Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706 (United States)

2014-08-28

Two intrinsic difficulties in modeling condensed-phase water with conventional rigid non-polarizable water models are: reproducing the static dielectric constants for liquid water and ice Ih, and generating the peak at about 200 cm{sup −1} in the low-frequency infrared spectrum for liquid water. The primary physical reason for these failures is believed to be the missing polarization effect in these models, and consequently various sophisticated polarizable water models have been developed. However, in this work we pursue a different strategy and propose a simple empirical scheme to include the polarization effect only on the dipole surface (without modifying a model's intermolecular interaction potential). We implement this strategy for our explicit three-body (E3B) model. Our calculated static dielectric constants and low-frequency infrared spectra are in good agreement with experiment for both liquid water and ice Ih over wide temperature ranges, albeit with one fitting parameter for each phase. The success of our modeling also suggests that thermal fluctuations about local minima and the energy differences between different proton-disordered configurations play minor roles in the static dielectric constant of ice Ih. Our analysis shows that the polarization effect is important in resolving the two difficulties mentioned above and sheds some light on the origin of several features in the low-frequency infrared spectra for liquid water and ice Ih.

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-12-09

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

Transformation Algorithm of Dielectric Response in Time-Frequency Domain

Directory of Open Access Journals (Sweden)

Ji Liu

2014-01-01

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

Multi-wavelength metal-dielectric nonpolarizing beam splitters in the near-infrared range

Science.gov (United States)

Hui Shi, Jin; Ping Wang, Zheng; Ying Guan, Chun; Yang, Jun; Shu Fu, Tian

2011-04-01

A 21-layer multi-wavelength metal-dielectric nonpolarizing cube beam splitter was designed by use of an optimization method and theoretically investigated in the near-infrared range. The angular dependence of the reflectance and differential phases induced by reflection and transmission were presented. The simulation results revealed that the non-polarizing effect could be achieved for both the amplitude and phase characteristics at 1310 and 1550 nm. The differences between the simulated and the target reflectance of 50% are less than 2% and differential phases are less than 5°in the range 1300-1320 nm and 1540-1550 nm for both p- and s-components.

Features of dielectric response in PMN-PT ferroelectric ceramics

International Nuclear Information System (INIS)

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

2008-01-01

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

Measurement of sugar content of watermelon using near-infrared reflectance spectroscopy in comparison with dielectric property

Science.gov (United States)

Tao, Xuemei; Bao, Yidan

2006-09-01

The sugar content of watermelon is important to its taste thus influences the market. It's difficult to know whether the melon is sweet or not for consumers. We tried to develop a convenient meter to determine the sugar of watermelon. The first objective of this paper was to demonstrate the feasibility of using a near-infrared reflectance spectrometer (NIRS) to investigate the relationship between sugar content of watermelon and absorption spectra. The NIRS reflectance of nondestructive watermelon was measured with a Visible/NIR spectrophotometer in 325-1075nm range. The sugar content of watermelon was obtained with a handhold sugar content meter. The second objective was to measure the watermelon's dielectric property, such as dielectric resistance, capacitance, quality factor and dielectric loss. A digital electric bridge instrument was used to get the dielectric property. The experimental results show that they were related to watermelon's sugar content. A comparison between the two methods was made in the paper. The model derived from NIRS reflection is useful for class identification of Zaochun Hongyu watermelon though it's not quite accurate in sweetness prediction (the max. deviation is 0.7). Electric property bears little relation to sugar content of watermelon at this experiment and it couldn't be used as non-destructive inspection method.

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

International Nuclear Information System (INIS)

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

2007-01-01

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

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

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.

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)

Electrical response of relaxing dielectrics compressed by arbitrary stress pulses

International Nuclear Information System (INIS)

Lysne, P.C.

1983-01-01

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

Insight into the dielectric response of transformer oil-based nanofluids

Directory of Open Access Journals (Sweden)

Ming Dong

2017-02-01

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

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...

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

International Nuclear Information System (INIS)

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

1995-01-01

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

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

Science.gov (United States)

Chong, Katie Eve

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

Dielectric response of planar relativistic quantum plasmas

International Nuclear Information System (INIS)

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

1991-01-01

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

Dielectric response in guiding center plasma

International Nuclear Information System (INIS)

Krommes, J.A.; Similon, P.

1979-12-01

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

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.

Design of planar chiral metamaterials for near-infrared regime

Science.gov (United States)

Kaya, Sabri; Turkmen, Mustafa; Topaktas, Omer

2017-01-01

Planar chiral metamaterials (PCMs) comprising double-layer dielectric-metal-dielectric resonant structures in the shape of a windmill are presented for near-infrared regime. The circular dichroism is retrieved from transmission spectra. Effects of used materials on circular dichroism characteristics of PCM arrays are investigated for the first time. The dependence of spectral characteristics on the geometrical parameters of the PCMs is analyzed by the finite-difference time-domain method. The observations indicated that the circular dichroism characteristics of the proposed PCM arrays are strongly dependent on the type of metal and dielectric materials. Due to the enhanced chiroptical near-field response and tunable spectral behavior, proposed PCM arrays may have potential for biosensing applications of chiral biomolecules.

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)

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.

Influence of poling on far-infrared response of lead zirconate titanate ceramics

Czech Academy of Sciences Publication Activity Database

Simon, E.; Hlinka, Jiří; Kamba, Stanislav; Gregora, Ivan; Erhart, J.

2009-01-01

Roč. 106, č. 7 (2009), 074104/1-074104/5 ISSN 0021-8979 R&D Projects: GA AV ČR KAN301370701; GA MŠk ME08109; GA ČR GA202/06/0411 Institutional research plan: CEZ:AV0Z10100520 Keywords : ceramics * dielectric polarisation * infrared spectra * lead compounds * phonons Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.072, year: 2009

Measurement of the quantity of water in organic solvents by infrared absorption an measurement of the dielectric constants

International Nuclear Information System (INIS)

Desnoyer, M.

1959-06-01

Some chemical methods for the analysis of the quantity of water in solvents are first described, their object being the determination of the maximum error for cases where the water content is less than 1 per cent. - The first part of the work consists in describing infrared spectrometry as applied to the analysis of water in carbon tetrachloride, chloroform aniline, acetone and dioxane. A method based on isotopic exchange between heavy and light water is used on the one hand for determining the solubility of water in carbon tetrachloride and on the other hand for establishing standard solutions (sensitivity of the method). - In the second part the dielectric constant of water solvent solutions is measured. A table is presented giving the precision obtained by the two principal methods. These are comparable and further than that the appearance of the spectra suggests an interpretation of the anomalies observed in calibration curves obtained by the dielectric constant method. (author) [fr

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...

Stability of the spectral responsivity of cryogenically cooled InSb infrared detectors

International Nuclear Information System (INIS)

Theocharous, Evangelos

2005-01-01

The spectral responsivity of two cryogenically cooled InSb detectors was observed to drift slowly with time. The origin of these drifts was investigated and was shown to occur due to a water-ice thin film that was deposited onto the active areas of the cold detectors. The presence of the ice film (which is itself a dielectric film) modifies the transmission characteristics of the antireflection coatings deposited on the active areas of the detectors, thus giving rise to the observed drifts. The magnitude of the drifts was drastically reduced by evacuating the detector dewars while baking them at 50 deg. C for approximately 48 h. All InSb detectors have antireflection coatings to reduce the Fresnel reflections and therefore enhance their spectral responsivity. This work demonstrates that InSb infrared detectors should be evacuated and baked at least annually and in some cases (depending on the quality of the dewar and the measurement uncertainty required) more frequently. These observations are particularly relevant to InSb detectors mounted in dewars that use rubber O rings since the ingress of moisture was found to be particularly serious in this type of dewar

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

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.

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.

Structural, optical and dielectric properties of graphene oxide

Science.gov (United States)

Bhargava, Richa; Khan, Shakeel

2018-05-01

The Modified Hummers method has been used to synthesize Graphene oxide nanoparticles. Microstructural analyses were carried out by X-ray diffraction and Fourier transform infrared spectroscopy. Optical properties were studied by UV-visible spectroscopy in the range of 200-700 nm. The energy band gap was calculated with the help of Tauc relation. The frequency dependence of dielectric constant and dielectric loss were studied over a range of the frequency 75Hz to 5MHz at room temperature. The dispersion in dielectric constant can be explained with the help of Maxwell-Wagner model in studied nanoparticles.

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.

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.

Dielectric response of periodic systems from quantum Monte Carlo calculations.

Science.gov (United States)

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

2005-11-11

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

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...

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.

Development of High-Gradient Dielectric Laser-Driven Particle Accelerator Structures

Energy Technology Data Exchange (ETDEWEB)

Byer, Robert L. [Stanford Univ., CA (United States). Edward L. Ginzton Lab.

2013-11-07

The thrust of Stanford's program is to conduct research on high-gradient dielectric accelerator structures driven with high repetition-rate, tabletop infrared lasers. The close collaboration between Stanford and SLAC (Stanford Linear Accelerator Center) is critical to the success of this project, because it provides a unique environment where prototype dielectric accelerator structures can be rapidly fabricated and tested with a relativistic electron beam.

Studies on metal-dielectric plasmonic structures.

Energy Technology Data Exchange (ETDEWEB)

Chettiar, Uday K. (Purdue University, West Lafayette, IN); Liu, Zhengtong (Purdue University, West Lafayette, IN); Thoreson, Mark D. (Purdue University, West Lafayette, IN); Shalaev, Vladimir M. (Purdue University, West Lafayette, IN); Drachev, Vladimir P. (Purdue University, West Lafayette, IN); Pack, Michael Vern; Kildishev, Alexander V. (Purdue University, West Lafayette, IN); Nyga, Piotr (Purdue University, West Lafayette, IN)

2010-01-01

The interaction of light with nanostructured metal leads to a number of fascinating phenomena, including plasmon oscillations that can be harnessed for a variety of cutting-edge applications. Plasmon oscillation modes are the collective oscillation of free electrons in metals under incident light. Previously, surface plasmon modes have been used for communication, sensing, nonlinear optics and novel physics studies. In this report, we describe the scientific research completed on metal-dielectric plasmonic films accomplished during a multi-year Purdue Excellence in Science and Engineering Graduate Fellowship sponsored by Sandia National Laboratories. A variety of plasmonic structures, from random 2D metal-dielectric films to 3D composite metal-dielectric films, have been studied in this research for applications such as surface-enhanced Raman sensing, tunable superlenses with resolutions beyond the diffraction limit, enhanced molecular absorption, infrared obscurants, and other real-world applications.

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.

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.

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

Czech Academy of Sciences Publication Activity Database

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

2004-01-01

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

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

Absorption in one-dimensional metallic-dielectric photonic crystals

International Nuclear Information System (INIS)

Yu Junfei; Shen Yifeng; Liu Xiaohan; Fu Rongtang; Zi Jian; Zhu Zhiqiang

2004-01-01

We show theoretically that the absorption of one-dimensional metallic-dielectric photonic crystals can be enhanced considerably over the corresponding constituent metal. By properly choosing the structural and material parameters, the absorption of one-dimensional metallic-dielectric photonic crystals can be enhanced by one order of magnitude in the visible and in the near infrared regions. It is found that the absorptance of such photonic crystals increases with increasing number of periods. Rules on how to obtain a absorption enhancement in a certain frequency range are discussed. (letter to the editor)

High energy-resolution electron energy-loss spectroscopy study of the dielectric properties of bulk and nanoparticle LaB6 in the near-infrared region

International Nuclear Information System (INIS)

Sato, Yohei; Terauchi, Masami; Mukai, Masaki; Kaneyama, Toshikatsu; Adachi, Kenji

2011-01-01

The dielectric properties of LaB 6 crystals and the plasmonic behavior of LaB 6 nanoparticles, which have been applied to solar heat-shielding filters, were studied by high energy-resolution electron energy-loss spectroscopy (HR-EELS). An EELS spectrum of a LaB 6 crystal showed a peak at 2.0 eV, which was attributed to volume plasmon excitation of carrier electrons. EELS spectra of single LaB 6 nanoparticles showed peaks at 1.1-1.4 eV depending on the dielectric effect from the substrates. The peaks were assigned to dipole oscillation excitations. These peak energies almost coincided with the peak energy of optical absorption of a heat-shielding filter with LaB 6 nanoparticles. On the other hand, those energies were a smaller than a dipole oscillation energy predicted using the dielectric function of bulk LaB 6 crystal. It is suggested that the lower energy than expected is due to an excitation at 1.2 eV, which was observed for oxidized LaB 6 area. -- Highlights: → The dielectric properties of LaB 6 nanoparticles applied to solar heat-shielding filters were studied by HR-EELS. → Plasmon peak energies of the LaB 6 nanoparticles were almost equal to optical absorption energy of a heat-shielding filter. → From this result, near-infrared optical absorption of the filter is due to the surface dipole mode of the nanoparticles.

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

Terahertz time-domain spectroscopy response of amines and amino acids intercalated smectites in far-infrared region

Energy Technology Data Exchange (ETDEWEB)

Janek, M., E-mail: marian.janek@fns.uniba.sk [Comenius University, Faculty of Natural Sciences, Department of Physical and Theoretical Chemistry, Mlynská dolina CH1, SK-84215 Bratislava (Slovakia); Zich, D. [Comenius University, Faculty of Natural Sciences, Department of Physical and Theoretical Chemistry, Mlynská dolina CH1, SK-84215 Bratislava (Slovakia); Naftaly, M., E-mail: mira.naftaly@npl.co.uk [National Physical Laboratory, Hampton Rd, Teddington, Middlesex TW11 0LW (United Kingdom)

2014-06-01

Layered clay minerals from the smectite group with different chemical composition and resulting layer charge (e.g. pyrophyllite, illite, hectorite and montmorillonite) were characterised for their dielectric properties in the far-infrared region using terahertz-time domain spectroscopy (THz-TDS). Samples with distinct cation exchange capacity such as hectorite and montmorillonite were modified using cation exchange reaction with alkylamines or amino acids. The presence of these species in 2D gallery was proved by X-ray diffraction and Fourier transform infrared spectroscopy. The frequency-dependent refractive index of these minerals was determined in the experimentally accessible range of 0.1–3.0 THz (3–100 cm{sup −1}) using THz-TDS. Pristine samples revealed their refractive indices to be 1.82–2.15 at about 1 THz while the modified montmorillonite samples had their refractive indices changed by organic molecules used for their modification to 1.70–2.35 for amines and 1.97–2.36 for amino acids. The presence of organic substances in 2D gallery of clays was detectable despite the relatively high absorption of smectites with magnitude of 100 cm{sup −1}. - Graphical abstract: Display Omitted - Highlights: • “Guest” molecules in “host” layered material were investigated. • Amines and amino-acids were selected as guest molecules. • Natural and synthetic host with smectite phyllosilicate structure were used. • Dielectric properties were investigated by terahertz time domain spectroscopy. • Resonance absorption peaks of guest were detected in far infrared region.

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

Czech Academy of Sciences Publication Activity Database

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

2006-01-01

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

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.

Infrared characterization of strontium titanate thin films

International Nuclear Information System (INIS)

Almeida, B.G.; Pietka, A.; Mendes, J.A.

2004-01-01

Strontium titanate thin films have been prepared at different oxygen pressures with various post-deposition annealing treatments. The films were deposited by pulsed laser ablation at room temperature on Si(0 0 1) substrates with a silica buffer layer. Infrared reflectance measurements were performed in order to determine relevant film parameters such as layer thicknesses and chemical composition. The infrared reflectance spectra were fitted by using adequate dielectric function forms for each layer. The fitting procedure provided the extraction of the dielectric functions of the strontium titanate film, the silica layer and the substrate. The as-deposited films are found to be amorphous, and their infrared spectra present peaks corresponding to modes with high damping constants. As the annealing time and temperature increases the strontium titanate layer becomes more ordered so that it can be described by its SrTiO 3 bulk mode parameters. Also, the silica layer grows along with the ordering of the strontium titanate film, due to oxidation during annealing

Dielectric properties of carbon nanofibre/alumina composites

Czech Academy of Sciences Publication Activity Database

Fernandez-Garcia, L.; Suarez, M.; Menéndez, J.L.; Pecharromán, C.; Nuzhnyy, Dmitry; Bovtun, Viktor; Savinov, Maxim; Kempa, Martin; Petzelt, Jan

2013-01-01

Roč. 57, JUN (2013), s. 380-387 ISSN 0008-6223 R&D Projects: GA ČR GAP204/12/0232; GA MŠk LD12025 Institutional support: RVO:68378271 Keywords : alumina * carbon nanofibre * dielectric and THz spectroscopy * infrared spectroscopy * percolation threshold Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 6.160, year: 2013

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

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.

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.

Effective dielectric functions of samples obtained by evaporation of alkali halides

International Nuclear Information System (INIS)

Sturm, J.; Grosse, P.; Theiss, W.

1991-01-01

This paper investigates the dielectric properties of inhomogeneous samples consisting of small alkali halide particles (NaCl, KBr) on gold-coated substrates. Our reflection measurements in the far infrared can be simulated as a thin layer of the power with an effective dielectric function on a perfectly reflecting substrate. Scanning electron micrographs provide useful information about sample topology. Several mixing formulas (e.g. the Maxwell-Garnett, the Bruggeman- and the Looyenga-formula) lead to effective dielectric functions neglecting the individual arrangement of the particles. The essence of our work is that, in contrast, the general ansatz of the Bergman spectral representation has to be employed in order to take into account topology effects on the dielectric function based on the so-called spectral density g adjustable to the specific situation. (orig.)

Far infrared and Raman response in tetragonal PZT ceramic films

Czech Academy of Sciences Publication Activity Database

Buixaderas, Elena; Kadlec, Christelle; Vaněk, Přemysl; Drnovšek, S.; Uršič, H.; Malič, B.

2015-01-01

Roč. 54, č. 6 (2015), s. 219-224 ISSN 0366-3175 R&D Projects: GA ČR(CZ) GA14-25639S Institutional support: RVO:68378271 Keywords : dielectric response * phonons * FIR spectroscopy * time-domain THz spectroscopy * Raman spectroscopy * effective medium * PZT Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.280, year: 2015

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)

Detuned-resonator induced transparency in dielectric-loaded plasmonic waveguides

DEFF Research Database (Denmark)

Han, Zhanghua; García Ortíz, César Eduardo; Radko, Ilya P.

2013-01-01

We report on the experimental demonstration of detuned-resonator induced transparency in the near-infrared (∼800  nm) using two detuned racetrack resonators side-coupled to a bus waveguide. Both resonators and the bus waveguide are in the form of dielectric-loaded surface plasmon polariton...

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.

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}.

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)

Attosecond control of electron beams at dielectric and absorbing membranes

Science.gov (United States)

Morimoto, Yuya; Baum, Peter

2018-03-01

Ultrashort electron pulses are crucial for time-resolved electron diffraction and microscopy of the fundamental light-matter interaction. In this work, we study experimentally and theoretically the generation and characterization of attosecond electron pulses by optical-field-driven compression and streaking at dielectric or absorbing interaction elements. The achievable acceleration and deflection gradient depends on the laser-electron angle, the laser's electric and magnetic field directions, and the foil orientation. Electric and magnetic fields have similar contributions to the final effect and both need to be considered. Experiments and theory agree well and reveal the optimum conditions for highly efficient, velocity-matched electron-field interactions in the longitudinal or transverse direction. We find that metallic membranes are optimum for light-electron control at mid-infrared or terahertz wavelengths, but dielectric membranes are excellent in the visible and near-infrared regimes and are therefore ideal for the formation of attosecond electron pulses.

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

The influence of various dielectric parameters on the reststrahlen region of SiC

International Nuclear Information System (INIS)

Engelbrecht, J.A.A.; Rooyen, I.J. van

2011-01-01

The reststrahlen region of SiC is analysed with the goal of establishing the origin of different shapes of this band, by varying the dielectric parameters involved when simulating the reststrahlen region as obtained by infrared reflectance. -- Research highlights: → An anomalous peak observed in the reststrahlen band of SiC was investigated. → The reflection spectrum of SiC in the reststrahlen region was simulated by theoretical calculations. → The influence on the reststrahlen band of the dielectric parameters used in the simulations is discussed. → Dielectric parameters used in the simulations did not yield the anomalous peak that is observed experimentally.

The influence of various dielectric parameters on the reststrahlen region of SiC

Energy Technology Data Exchange (ETDEWEB)

Engelbrecht, J.A.A., E-mail: Japie.Engelbrecht@nmmu.ac.z [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); Rooyen, I.J. van [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); National Laser Centre, CSIR, PO Box 395, Pretoria 0001 (South Africa)

2011-02-01

The reststrahlen region of SiC is analysed with the goal of establishing the origin of different shapes of this band, by varying the dielectric parameters involved when simulating the reststrahlen region as obtained by infrared reflectance. -- Research highlights: {yields} An anomalous peak observed in the reststrahlen band of SiC was investigated. {yields} The reflection spectrum of SiC in the reststrahlen region was simulated by theoretical calculations. {yields} The influence on the reststrahlen band of the dielectric parameters used in the simulations is discussed. {yields} Dielectric parameters used in the simulations did not yield the anomalous peak that is observed experimentally.

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.

Porogen residues detection in optical properties of low-k dielectrics cured by ultraviolet radiation

Energy Technology Data Exchange (ETDEWEB)

Marsik, Premysl, E-mail: marsik@physics.muni.c [UFKL, Masaryk University, Kotlarska 2, 61137 Brno (Czech Republic); IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Verdonck, Patrick [IMEC, Kapeldreef 75, 3001 Leuven (Belgium); De Roest, David [ASM Belgium, Kapeldreef 75, 3001 Leuven (Belgium); Baklanov, Mikhail R. [IMEC, Kapeldreef 75, 3001 Leuven (Belgium)

2010-05-31

The optical properties of low dielectric constant (low-k) films have been determined by variable angle spectroscopic ellipsometry in the range from 2 eV to 9 eV to characterize the process of porogen removal during the UV-cure. The studied carbon doped oxide (SiCOH) porous dielectric films have been prepared by plasma enhanced chemical vapor deposition. The films have been deposited as a composition of a matrix precursor and an organic porogen. After deposition, the films have been cured by thermal annealing and UV irradiation ({lambda} = 172 nm) to remove the porogen and create a porosity of 33%, reaching a dielectric constant of 2.3. The process of porogen decomposition and removal has been studied on series of low-k samples, UV-cured for various times. Additional samples have been prepared by the deposition and curing of the porogen film, without SiCOH matrix, and the matrix material itself, without porogen. The analysis of the optical response of the porous dielectric as a mixture of matrix material, porogen and voids, together with Fourier transform infrared analysis, allows the sensitive detection of the volume of the porogen and indicates the existence of decomposed porogen residues inside the pores, even for long curing time. The variation of the deposition and curing conditions can control the amount of the porogen residues and the final porosity.

Radiation response issues for infrared detectors

Science.gov (United States)

Kalma, Arne H.

1990-01-01

Researchers describe the most important radiation response issues for infrared detectors. In general, the two key degradation mechanisms in infrared detectors are the noise produced by exposure to a flux of ionizing particles (e.g.; trapped electronics and protons, debris gammas and electrons, radioactive decay of neutron-activated materials) and permanent damage produced by exposure to total dose. Total-dose-induced damage is most often the result of charge trapping in insulators or at interfaces. Exposure to short pulses of ionization (e.g.; prompt x rays or gammas, delayed gammas) will cause detector upset. However, this upset is not important to a sensor unless the recovery time is too long. A few detector technologies are vulnerable to neutron-induced displacement damage, but fortunately most are not. Researchers compare the responses of the new technologies with those of the mainstream technologies of PV HgCdTe and IBC Si:As. One important reason for this comparison is to note where some of the newer technologies have the potential to provide significantly improved radiation hardness compared with that of the mainstream technologies, and thus to provide greater motivation for the pursuit of these technologies.

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)

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

Study of the dielectric properties of barium titanate-polymer composites

International Nuclear Information System (INIS)

Pant, H.C.; Patra, M.K.; Verma, Aditya; Vadera, S.R.; Kumar, N.

2006-01-01

A comparative study of complex dielectric properties has been carried out at the X-band of microwave frequencies of composites of barium titanate (BaTiO 3 ) with two different polymer matrices: insulating polyaniline (PANI) powder (emeraldine base) and maleic resin. From these studies, it is observed that the composites of BaTiO 3 with maleic resin show normal composite behavior and the dielectric constant follows the asymmetric Bruggeman model. In contrast, the composites of BaTiO 3 with PANI show an unusual behavior wherein even at a low concentration of PANI (5 wt.%) there is a drastic reduction in the dielectric constant of BaTiO 3 . This behavior of the dielectric constant is explained on the basis of coating of BaTiO 3 particles by PANI which in turn is attributed to the highly surface adsorbing character. The materials have also been characterized using Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy and optical microscopy studies

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.

The flexoelectric effect associated size dependent pyroelectricity in solid dielectrics

Science.gov (United States)

Bai, Gang; Liu, Zhiguo; Xie, Qiyun; Guo, Yanyan; Li, Wei; Yan, Xiaobing

2015-09-01

A phenomenological thermodynamic theory is used to investigate the effect of strain gradient on the pyroelectric effect in centrosymmetric dielectric solids. Direct pyroelectricity can exist as external mechanical stress is applied to non-pyroelectric dielectrics with shapes such as truncated pyramids, due to elastic strain gradient induced flexoelectric polarization. Effective pyroelectric coefficient was analyzed in truncated pyramids. It is found to be controlled by size, ambient temperature, stress, and aspect ratio and depends mainly on temperature sensitivity of flexoelectric coefficient (TSFC) and strain gradient of the truncated pyramids dielectric solids. These results show that the pyroelectric property of Ba0.67Sr0.33TiO3 above Tc similar to PZT and other lead-based ferroelectrics can be obtained. This feature might widely broaden the selection of materials for infrared detectors with preferable properties.

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.

Broadband dielectric spectroscopy of standard and core-shell BaTiO.sub.3./sub.-NiO ceramic composites compared to the BaTiO.sub.3./sub. ceramics

Czech Academy of Sciences Publication Activity Database

Nuzhnyy, Dmitry; Petzelt, Jan; Bovtun, Viktor; Ostapchuk, Tetyana; Savinov, Maxim; Kempa, Martin; Bednyakov, Petr; Fernández-Garciá, L.; Rodriguez-Suarez, T.; Menendéz, J.L.

2016-01-01

Roč. 500, č. 1 (2016), s. 1-19 ISSN 0015-0193 R&D Projects: GA ČR GA15-08389S Institutional support: RVO:68378271 Keywords : core-shell composite * effective dielectric function * effective infrared response * effective medium approximation * percolation * barium titanate * nickel oxide Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.551, year: 2016

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...

Low-Loss, Low-Noise, Crystalline Silicon Dielectric for Superconducting Microstrip and Kinetic Inductance Detector Capacitors

Data.gov (United States)

National Aeronautics and Space Administration — Development of technology to use crystalline dielectrics in superconducting spectroscopic sensors operating in the infrared/sub-millimeter wavelength range. The...

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.

The flexoelectric effect associated size dependent pyroelectricity in solid dielectrics

Energy Technology Data Exchange (ETDEWEB)

Bai, Gang, E-mail: baigang@njupt.edu.cn [Jiangsu Provincial Engineering Laboratory for RF Integration and Micropackaging and College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023 (China); Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Liu, Zhiguo [Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Xie, Qiyun; Guo, Yanyan; Li, Wei [Jiangsu Provincial Engineering Laboratory for RF Integration and Micropackaging and College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023 (China); Yan, Xiaobing [College of Electronic and information Engineering, Hebei University, Baoding 071002 (China)

2015-09-15

A phenomenological thermodynamic theory is used to investigate the effect of strain gradient on the pyroelectric effect in centrosymmetric dielectric solids. Direct pyroelectricity can exist as external mechanical stress is applied to non-pyroelectric dielectrics with shapes such as truncated pyramids, due to elastic strain gradient induced flexoelectric polarization. Effective pyroelectric coefficient was analyzed in truncated pyramids. It is found to be controlled by size, ambient temperature, stress, and aspect ratio and depends mainly on temperature sensitivity of flexoelectric coefficient (TSFC) and strain gradient of the truncated pyramids dielectric solids. These results show that the pyroelectric property of Ba{sub 0.67}Sr{sub 0.33}TiO{sub 3} above T{sub c} similar to PZT and other lead-based ferroelectrics can be obtained. This feature might widely broaden the selection of materials for infrared detectors with preferable properties.

Multichannel far-infrared phase imaging for fusion plasmas

International Nuclear Information System (INIS)

Young, P.E.; Neikirk, D.P.; Tong, P.P.; Rutledge, D.B.; Luhmann, N.C. Jr.

1985-01-01

A 20-channel far-infrared imaging interferometer system has been used to obtain single-shot density profiles in the UCLA Microtor tokamak. This system differs from conventional multichannel interferometers in that the phase distribution produced by the plasma is imaged onto a single, monolithic, integrated microbolometer linear detector array and provides significantly more channels than previous far-infrared interferometers. The system has been demonstrated to provide diffraction-limited phase images of dielectric targets

Study of the dielectric properties of barium titanate-polymer composites

Energy Technology Data Exchange (ETDEWEB)

Pant, H.C. [R and D Laboratory, Defence Laboratory, Camouflage Division, Defence Laboratory Ratanada Palace, Jodhpur 342011, Rajasthan (India); Patra, M.K. [R and D Laboratory, Defence Laboratory, Camouflage Division, Defence Laboratory Ratanada Palace, Jodhpur 342011, Rajasthan (India); Verma, Aditya [R and D Laboratory, Defence Laboratory, Camouflage Division, Defence Laboratory Ratanada Palace, Jodhpur 342011, Rajasthan (India); Vadera, S.R. [R and D Laboratory, Defence Laboratory, Camouflage Division, Defence Laboratory Ratanada Palace, Jodhpur 342011, Rajasthan (India); Kumar, N. [R and D Laboratory, Defence Laboratory, Camouflage Division, Defence Laboratory Ratanada Palace, Jodhpur 342011, Rajasthan (India)]. E-mail: nkjainjd@yahoo.com

2006-07-15

A comparative study of complex dielectric properties has been carried out at the X-band of microwave frequencies of composites of barium titanate (BaTiO{sub 3}) with two different polymer matrices: insulating polyaniline (PANI) powder (emeraldine base) and maleic resin. From these studies, it is observed that the composites of BaTiO{sub 3} with maleic resin show normal composite behavior and the dielectric constant follows the asymmetric Bruggeman model. In contrast, the composites of BaTiO{sub 3} with PANI show an unusual behavior wherein even at a low concentration of PANI (5 wt.%) there is a drastic reduction in the dielectric constant of BaTiO{sub 3}. This behavior of the dielectric constant is explained on the basis of coating of BaTiO{sub 3} particles by PANI which in turn is attributed to the highly surface adsorbing character. The materials have also been characterized using Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy and optical microscopy studies.

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.

Polymethyl methacrylate (PMMA)-bismuth ferrite (BFO) nanocomposite: low loss and high dielectric constant materials with perceptible magnetic properties.

Science.gov (United States)

Tamboli, Mohaseen S; Palei, Prakash K; Patil, Santosh S; Kulkarni, Milind V; Maldar, Noormahmad N; Kale, Bharat B

2014-09-21

Herein, poly(methyl methacrylate)-bismuth ferrite (PMMA-BFO) nanocomposites were successfully prepared by an in situ polymerization method for the first time. Initially, the as prepared bismuth ferrite (BFO) nanoparticles were dispersed in the monomer, (methyl methacrylate) by sonication. Benzoyl peroxide was used to initiate the polymerization reaction in ethyl acetate medium. The nanocomposite films were subjected to X-ray diffraction analysis (XRD), (1)H NMR, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), infrared spectroscopy (IR), dielectric and magnetic characterizations. The dielectric measurement of the nanocomposites was investigated at a frequency range of 10 Hz to 1 MHz. It was found that the nanocomposites not only showed a significantly increased value of the dielectric constant with an increase in the loading percentage of BFO as compared to pure PMMA, but also exhibited low dielectric loss values over a wide range of frequencies. The values of the dielectric constant and dielectric loss of the PMMA-BFO5 (5% BFO loading) sample at 1 kHz frequency was found be ~14 and 0.037. The variation of the ferromagnetic response of the nanocomposite was consistent with the varying volume percentage of the nanoparticles. The remnant magnetization (Mr) and saturation magnetization (Ms) values of the composites were found to be enhanced by increasing the loading percentage of BFO. The value of Ms for PMMA-BFO5 was found to be ~6 emu g(-1). The prima facie observations suggest that the nanocomposite is a potential candidate for application in high dielectric constant capacitors. Significantly, based on its magnetic properties the composite will also be useful for use in hard disk components.

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.

Semiconductor-to-metallic flipping in a ZnFe2O4–graphene based smart nano-system: Temperature/microwave magneto-dielectric spectroscopy

International Nuclear Information System (INIS)

Ameer, Shahid; Gul, Iftikhar Hussain; Mahmood, Nasir; Mujahid, Muhammad

2015-01-01

Zn-(FeO 2 ) 2 –graphene smart nano-composites were synthesized using a novel modified solvothermal synthesis with different percentages of graphene. The structure of the nanocomposite was confirmed through X-ray diffraction, micro-Raman scattering spectroscopy, Ultraviolet–Visible spectroscopy, and Fourier transform infrared spectroscopy. The structural growth and morphological aspects were analyzed using scanning/transmission electron microscopy, revealing marvelous micro-structural features of the assembled nano-system resembling a maple leaf. To determine the composition, energy dispersive spectroscopy and X-ray photoelectron spectroscopy were used. Microwave magneto-dielectric spectroscopy revealed the improved dielectric properties of the nano-composite compared to those of the parent functional nanocrystals. Temperature gradient dielectric spectroscopy was used over the spectral range from 100 Hz to 5 MHz to reveal the phenomenological effect that the nanosystem flips from its usual semiconductor nature to a metallic nature with sensing temperature. Electrical conductivity and dielectric analysis indicated that the dielectric loss and the dielectric permittivity increased at room temperature. This extraordinary switching capability of the functionalized graphene nanosystem opens up a new dimension for engineering advanced and efficient smart composite materials. - Graphical abstract: Display Omitted - Highlights: • Zn-(FeO 2 ) 2 –graphene smart nano-composites were synthesized using a novel modified solvothermal synthesis. • The synthesized nano-system exhibits marvelous leaf like microstructure. • These nano-composites show improved magneto dielectric response. • This engineered smart nano-system shows phenomenological flipping from semiconductor like nature to metallic behavior

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

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 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

The apparent effect of sample surface damage on the dielectric parameters of GaAs

Energy Technology Data Exchange (ETDEWEB)

Engelbrecht, J.A.A. [Physics Department, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa)], E-mail: Japie.Engelbrecht@nmmu.ac.za; Hashe, N.G. [Physics Department, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Hillie, K.T. [CSIR-NML Laboratory, P.O. Box 395, Pretoria 0001 (South Africa); Claassens, C.H. [Physics Department, University of the Free State, Bloemfontein 9300 (South Africa)

2007-12-15

The dielectric and optical parameters determined by infrared reflectance spectroscopy and computer simulation of a set of GaAs substrates of various surface topologies are reported. The influence of surface damage on the parameters is noted.

The apparent effect of sample surface damage on the dielectric parameters of GaAs

International Nuclear Information System (INIS)

Engelbrecht, J.A.A.; Hashe, N.G.; Hillie, K.T.; Claassens, C.H.

2007-01-01

The dielectric and optical parameters determined by infrared reflectance spectroscopy and computer simulation of a set of GaAs substrates of various surface topologies are reported. The influence of surface damage on the parameters is noted

High-Efficiency Dielectric Metasurfaces for Polarization-Dependent Terahertz Wavefront Manipulation

KAUST Repository

Zhang, Huifang

2017-11-30

Recently, metasurfaces made up of dielectric structures have drawn enormous attentions in the optical and infrared regimes due to their high efficiency and designing freedom in manipulating light propagation. Such advantages can also be introduced to terahertz frequencies where efficient functional devices are still lacking. Here, polarization-dependent all-silicon terahertz dielectric metasurfaces are proposed and experimentally demonstrated. The metasurfaces are composed of anisotropic rectangular-shaped silicon pillars on silicon substrate. Each metasurface holds dual different functions depending on the incident polarizations. Furthermore, to suppress the reflection loss and multireflection effect in practical applications, a high-performance polarization-independent antireflection silicon pillar array is also proposed, which can be patterned at the other side of the silicon substrate. Such all-silicon dielectric metasurfaces are easy to fabricate and can be very promising in developing next-generation efficient, compact, and low-cost terahertz functional devices.

Sintering and dielectric properties of a technical porcelain prepared from economical natural raw materials

Directory of Open Access Journals (Sweden)

S. Kasrani

Full Text Available Abstract In this study, the production of a technical porcelain, for the ceramic dielectric applications by using economical natural raw materials, was investigated. The basic porcelain composition was selected consisting of 30 wt% kaolin, 45 wt% potash-feldspar and 25 wt% quartz. The obtained phases in the sintered samples were investigated by X-ray diffraction, Fourier transform infrared spectroscopy analysis, and scanning electron microscopy images. It has been confirmed by these techniques that the main crystalline phases were quartz and mullite. Dielectric measurements of technical porcelains have been carried out at 1 kHz from room temperature to 200 °C. The dielectric constant, loss factor, dielectric loss tangent, and resistivity of the porcelain sample sintered at 1160 °C were 22-25, 0.32-1.80, 0.006-0.07, and 0.2-9 x 1013 Ω.cm, respectively. The value of dielectric constant was significantly high when compared to that of conventional porcelains which did not exceed generally 9.

Sintering and dielectric properties of a technical porcelain prepared from economical natural raw materials

Energy Technology Data Exchange (ETDEWEB)

Kasrani, S.; Harabi, A.; Barama, S.-E.; Foughali, L.; Benhassine, M. T., E-mail: souad478@yahoo.fr, E-mail: harabi52@gmail.com, E-mail: sebarama@usa.com, E-mail: foughali_lazhar@yahoo.fr, E-mail: mtb25dz@gmail.com [Ceramics Lab. Mentouri University of Constantine (Algeria); Aldhayan, D.M., E-mail: aldhayan@ksu.edu.sa [Chemistry Department, Riyadh, King Saud University (Saudi Arabia)

2016-10-15

In this study, the production of a technical porcelain, for the ceramic dielectric applications by using economical natural raw materials, was investigated. The basic porcelain composition was selected consisting of 30 wt% kaolin, 45 wt% potash-feldspar and 25 wt% quartz. The obtained phases in the sintered samples were investigated by X-ray diffraction, Fourier transform infrared spectroscopy analysis, and scanning electron microscopy images. It has been confirmed by these techniques that the main crystalline phases were quartz and mullite. Dielectric measurements of technical porcelains have been carried out at 1 kHz from room temperature to 200 °C. The dielectric constant, loss factor, dielectric loss tangent, and resistivity of the porcelain sample sintered at 1160 °C were 22-25, 0.32-1.80, 0.006-0.07, and 0.2-9 x 10{sup 13} Ω.cm, respectively. The value of dielectric constant was significantly high when compared to that of conventional porcelains which did not exceed generally 9. (author)

Sintering and dielectric properties of a technical porcelain prepared from economical natural raw materials

International Nuclear Information System (INIS)

Kasrani, S.; Harabi, A.; Barama, S.-E.; Foughali, L.; Benhassine, M. T.; Aldhayan, D.M.

2016-01-01

In this study, the production of a technical porcelain, for the ceramic dielectric applications by using economical natural raw materials, was investigated. The basic porcelain composition was selected consisting of 30 wt% kaolin, 45 wt% potash-feldspar and 25 wt% quartz. The obtained phases in the sintered samples were investigated by X-ray diffraction, Fourier transform infrared spectroscopy analysis, and scanning electron microscopy images. It has been confirmed by these techniques that the main crystalline phases were quartz and mullite. Dielectric measurements of technical porcelains have been carried out at 1 kHz from room temperature to 200 °C. The dielectric constant, loss factor, dielectric loss tangent, and resistivity of the porcelain sample sintered at 1160 °C were 22-25, 0.32-1.80, 0.006-0.07, and 0.2-9 x 10 13 Ω.cm, respectively. The value of dielectric constant was significantly high when compared to that of conventional porcelains which did not exceed generally 9. (author)

Design of a sector bowtie nano-rectenna for optical power and infrared detection

Science.gov (United States)

Wang, Kai; Hu, Haifeng; Lu, Shan; Guo, Lingju; He, Tao

2015-10-01

We designed a sector bowtie nanoantenna integrated with a rectifier (Au-TiO x -Ti diode) for collecting infrared energy. The optical performance of the metallic bowtie nanoantenna was numerically investigated at infrared frequencies (5-30 μm) using three-dimensional frequency-domain electromagnetic field calculation software based on the finite element method. The simulation results indicate that the resonance wavelength and local field enhancement are greatly affected by the shape and size of the bowtie nanoantenna, as well as the relative permittivity and conductivity of the dielectric layer. The output current of the rectified nano-rectenna is substantially at nanoampere magnitude with an electric field intensity of 1 V/m. Moreover, the power conversion efficiency for devices with three different substrates illustrates that a substrate with a larger refractive index yields a higher efficiency and longer infrared response wavelength. Consequently, the optimized structure can provide theoretical support for the design of novel optical rectennas and fabrication of optoelectronic devices.

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.

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.

Graphene metascreen for designing compact infrared absorbers with enhanced bandwidth

KAUST Repository

Chen, Pai-Yen

2015-03-31

We propose a compact, wideband terahertz and infrared absorber, comprising a patterned graphene sheet on a thin metal-backed dielectric slab. This graphene-based nanostructure can achieve a low or negative effective permeability, necessary for realizing the perfect absorption. The dual-reactive property found in both the plasmonic graphene sheet and the grounded highpermittivity slab introduces extra poles into the equivalent circuit model of the system, thereby resulting in a dual-band or broadband magnetic resonance that enhances the absorption bandwidth. More interestingly, the two-dimensional patterned graphene sheet significantly simplifies the design and fabrication processes for achieving resonant magnetic response, and allows the frequency-reconfigurable operation via electrostatic gating.

Graphene metascreen for designing compact infrared absorbers with enhanced bandwidth

KAUST Repository

Chen, Pai-Yen; Farhat, Mohamed; Bagci, Hakan

2015-01-01

We propose a compact, wideband terahertz and infrared absorber, comprising a patterned graphene sheet on a thin metal-backed dielectric slab. This graphene-based nanostructure can achieve a low or negative effective permeability, necessary for realizing the perfect absorption. The dual-reactive property found in both the plasmonic graphene sheet and the grounded highpermittivity slab introduces extra poles into the equivalent circuit model of the system, thereby resulting in a dual-band or broadband magnetic resonance that enhances the absorption bandwidth. More interestingly, the two-dimensional patterned graphene sheet significantly simplifies the design and fabrication processes for achieving resonant magnetic response, and allows the frequency-reconfigurable operation via electrostatic gating.

Enhancing the Responsivity of Uncooled Infrared Detectors Using Plasmonics for High-Performance Infrared Spectroscopy

Directory of Open Access Journals (Sweden)

Amr Shebl Ahmed

2017-04-01

Full Text Available A lead zirconate titanate (PZT;Pb(Zr0.52Ti0.48O3 layer embedded infrared (IR detector decorated with wavelength-selective plasmonic crystals has been investigated for high-performance non-dispersive infrared (NDIR spectroscopy. A plasmonic IR detector with an enhanced IR absorption band has been designed based on numerical simulations, fabricated by conventional microfabrication techniques, and characterized with a broadly tunable quantum cascade laser. The enhanced responsivity of the plasmonic IR detector at specific wavelength band has improved the performance of NDIR spectroscopy and pushed the limit of detection (LOD by an order of magnitude. In this paper, a 13-fold enhancement in the LOD of a methane gas sensing using NDIR spectroscopy is demonstrated with the plasmonic IR detector.

Ordinary dielectric function of corundumlike α -Ga2O3 from 40 meV to 20 eV

Science.gov (United States)

Feneberg, Martin; Nixdorf, Jakob; Neumann, Maciej D.; Esser, Norbert; Artús, Lluis; Cuscó, Ramon; Yamaguchi, Tomohiro; Goldhahn, Rüdiger

2018-04-01

The linear optical response of metastable α -Ga2O3 is investigated by spectroscopic ellipsometry. We determine the ordinary dielectric function from lattice vibrations up to the vacuum ultraviolet spectral range at room temperature for a sample with a (0001 ) surface. Three out of four Eu infrared-active phonon modes are unambiguously determined, and their frequencies are in good agreement with density functional theory calculations. The dispersion of the refractive index in the visible and ultraviolet part of the spectrum is determined. High-energy interband transitions are characterized up to 20 eV . By comparison with the optical response of α -Al2O3 and with theoretical results, a tentative assignment of interband transitions is proposed.

Controlling plasmonic properties of epitaxial thin films of indium tin oxide in the near-infrared region

Science.gov (United States)

Kamakura, R.; Fujita, K.; Murai, S.; Tanaka, K.

2015-06-01

Epitaxial thin films of indium tin oxide (ITO) were grown on yttria-stabilized zirconia single-crystal substrates by using a pulsed laser deposition to examine their plasmonic properties. The dielectric function of ITO was characterized by spectroscopic ellipsometry. Through the concentration of SnO2 in the target, the carrier concentration in the films was modified, which directly leads to the tuning of the dielectric function in the near-infrared region. Variable-angle reflectance spectroscopy in the Kretschmann geometry shows the dip in the reflection spectrum of p-polarized light corresponding to the excitation of surface plasmon polaritions (SPPs) in the near-infrared region. The excitation wavelength of the SPPs was shifted with changing the dielectric functions of ITO, which is reproduced by the calculation using transfer matrix method.

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 response of YBa2Cu3O7-δ films to pulsed, broadband synchrotron radiation

International Nuclear Information System (INIS)

Carr, G.L.; Quijada, M.; Tanner, D.B.; Etemad, S.; DeRosa, F.; Venkatesan, T.; Dutta, B.; Hemmick, D.; Xi, X.

1990-01-01

We report studies of a thin high T c film operating as a fast bolometric detector of infrared radiation. The film has a response of infrared radiation. The film has a response of several mV when exposed to a 1 W, 1 ns duration broadband infrared pulse. The decay after the pulse was about 4 ns. The temperature dependence of the response accurately tracked dR/dT. A thermal model, in which the film's temperature varies relative to the substrate, provides a good description of the response. We find no evidence for other (non-bolometric) response mechanisms for temperatures near or well below T c . 13 refs., 4 figs

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.

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

International Nuclear Information System (INIS)

Qian, H.; Bursill, L.A.

1997-01-01

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

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.

Inter-atomic bonding and dielectric polarization in Gd"3"+ incorporated Co-Zn ferrite nanoparticles

International Nuclear Information System (INIS)

Pawar, R.A.; Desai, S.S.; Patange, S.M.; Jadhav, S.S.; Jadhav, K.M.

2017-01-01

A series of ferrite with a chemical composition Co_0_._7Zn_0_._3Gd_xFe_2_−_xO_4 (where x=0.0 to x=0.1) were prepared by sol-gel auto-combustion method. X-ray diffraction pattern were used to determine the crystal structure and phase formation of the prepared samples. Scanning electron microscopy is used to study the surface morphology of the prepared samples. Elastic properties were determined from the infrared spectroscopy. Debye temperature, wave velocities, elastic constants found to increase with the increase in Gd"3"+ substitution. Dielectric properties such as dielectric constant and dielectric loss were studied as a function of Gd"3"+ substitution and frequency. Dielectric constant decreased with the increase in frequency and Gd"3"+ substitution. Behavior of dielectric properties was explained on the basis of Maxwell-Wagner interfacial polarization which in accordance with Koops phenomenological theory. Real and imaginary part of impedance was studied as a function of resistance and Gd"3"+ substitution. The behavior of impedance is systematically discussed on the basis of resistance-capacitance circuit.

Structural and dielectric properties of yttrium-substituted hydroxyapatites

Energy Technology Data Exchange (ETDEWEB)

Kaygili, Omer, E-mail: okaygili@firat.edu.tr [Department of Physics, Faculty of Science, Firat University, 23119 Elazig (Turkey); Dorozhkin, Sergey V. [Kudrinskaja sq. 1-155, 123242 Moscow (Russian Federation); Ates, Tankut [Department of Physics, Faculty of Science, Firat University, 23119 Elazig (Turkey); Canan Gursoy, N. [Department of Microbiology and Clinic Microbiology, Inonu University, 44280 Malatya (Turkey); Keser, Serhat [Department of Chemistry, Faculty of Science, Firat University, 23119 Elazig (Turkey); Yakuphanoglu, Fahrettin [Department of Physics, Faculty of Science, Firat University, 23119 Elazig (Turkey); Birkan Selçuk, A. [Technology Department, Saraykoy Nuclear Research and Training Centre, 06983 Ankara (Turkey)

2015-02-01

Hydroxyapatite (HAp) samples doped with 0, 2 and 4 at.% of yttrium (Y) were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy attached with energy dispersive X-ray (EDX) spectroscopy, antimicrobial activity tests and dielectric studies. The hydroxyl groups observed in FTIR spectra confirmed the formation of HAp phase in the studied samples. The crystallite size, crystallinity degree and lattice parameters of the samples were changed with Y content. The volume of the unit cell was gradually decreased with the addition of Y. Undoped and Y-containing HAp samples were screened to determine their in vitro antimicrobial activities against the standard strains. It was found that no samples have any antimicrobial effect. The relative dielectric permittivity and dielectric loss are affected by Y content. While the alternating current conductivity increases with increasing frequency, it decreases with increasing Y content. - Highlights: • The lattice parameters and crystal size are affected by Y content. • The volume of the unit cell was gradually decreased with the addition of Y. • No samples have any antimicrobial effect. • The alternating current conductivity decreases with increasing Y content.

Structural and dielectric properties of yttrium-substituted hydroxyapatites

International Nuclear Information System (INIS)

Kaygili, Omer; Dorozhkin, Sergey V.; Ates, Tankut; Canan Gursoy, N.; Keser, Serhat; Yakuphanoglu, Fahrettin; Birkan Selçuk, A.

2015-01-01

Hydroxyapatite (HAp) samples doped with 0, 2 and 4 at.% of yttrium (Y) were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy attached with energy dispersive X-ray (EDX) spectroscopy, antimicrobial activity tests and dielectric studies. The hydroxyl groups observed in FTIR spectra confirmed the formation of HAp phase in the studied samples. The crystallite size, crystallinity degree and lattice parameters of the samples were changed with Y content. The volume of the unit cell was gradually decreased with the addition of Y. Undoped and Y-containing HAp samples were screened to determine their in vitro antimicrobial activities against the standard strains. It was found that no samples have any antimicrobial effect. The relative dielectric permittivity and dielectric loss are affected by Y content. While the alternating current conductivity increases with increasing frequency, it decreases with increasing Y content. - Highlights: • The lattice parameters and crystal size are affected by Y content. • The volume of the unit cell was gradually decreased with the addition of Y. • No samples have any antimicrobial effect. • The alternating current conductivity decreases with increasing Y content

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

PREFACE: Dielectrics 2009: Measurement Analysis and Applications

Science.gov (United States)

Vaughan, Alun; Williams, Graham

2009-07-01

College, Dublin. The Meeting discussed dielectric relaxation behaviour arising from molecular motions of dipolar molecules in the liquid and elastomeric states (now known as soft condensed matter) with measurements spanning a frequency range from a few Hz, through power and radiofrequencies, UHF and VHF, the microwave range and into the far infra-red. As a result of its success, it was decided at the Meeting that a continuing Dielectrics Discussion Group would be established to meet not more frequently than once a year. It was appreciated at the time that the subject of 'Dielectrics' covered many sub-areas, broadly classified into those of polarization, relaxation, conduction and high-field phenomena. For the DDG, a solution was to run annual meetings on chosen themes in dielectrics research, where the theme would change from one meeting to the next. Topics addressed in the early years of the DDG included high field phenomena and impurity effects, heterogeneous systems and biomaterials, polarization and conduction and non-linear dielectrics and ferroelectrics. The number of participants at these early meetings grew from 50 to the low 100's, which reflected both the increased awareness of the Group and increased participation from researchers in Continental Europe. However, the majority of participants in this period were from the UK, which reflected the considerable activities in dielectrics research in University, Industry and Government laboratories in the UK. There followed a series of DDG Meetings until 1974, at which point, the DDG became a registered charity: The Dielectrics Society. Many of the earlier meetings were held in the attractive and convenient venues of Oxford and Cambridge colleges but, in the early 1990's, a new venue for the meetings was established at the University of Kent at Canterbury. In 2001, the next major change occurred when The Dielectrics Society was incorporated into the Institute of Physics, becoming their Dielectrics Group. From 1968 to

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.

Broadband dielectric spectroscopy of oxidized porous silicon

International Nuclear Information System (INIS)

Axelrod, Ekaterina; Urbach, Benayahu; Sa'ar, Amir; Feldman, Yuri

2006-01-01

Dielectric measurements accompanied by infrared absorption and photoluminescence (PL) spectroscopy were used to investigate the electrical and optical properties of oxidized porous silicon (PS). As opposed to non-oxidized PS, only high temperature relaxation processes could be resolved for oxidized PS. Two relaxation processes have been observed. The first process is related to dc-conductivity that dominates at high temperatures and low frequencies. After subtraction of dc-conductivity we could analyse a second high-temperature relaxation process that is related to interface polarization induced by charge carriers trapped at the host matrix-pore interfaces. We found that, while the main effect of the oxidation on the PL appears to be a size reduction in the silicon nanocrystals that gives rise to a blue shift of the PL spectrum, its main contribution to the dielectric properties turns out to be blocking of transport channels in the host tissue and activation of hopping conductivity between silicon nanocrystals

Broadband dielectric spectroscopy of oxidized porous silicon

Energy Technology Data Exchange (ETDEWEB)

Axelrod, Ekaterina [Department of Applied Physics, Hebrew University of Jerusalem, Jerusalem, 91904 (Israel); Urbach, Benayahu [Racah Institute of Physics and the Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Jerusalem, 91904 (Israel); Sa' ar, Amir [Racah Institute of Physics and the Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem, Jerusalem, 91904 (Israel); Feldman, Yuri [Department of Applied Physics, Hebrew University of Jerusalem, Jerusalem, 91904 (Israel)

2006-04-07

Dielectric measurements accompanied by infrared absorption and photoluminescence (PL) spectroscopy were used to investigate the electrical and optical properties of oxidized porous silicon (PS). As opposed to non-oxidized PS, only high temperature relaxation processes could be resolved for oxidized PS. Two relaxation processes have been observed. The first process is related to dc-conductivity that dominates at high temperatures and low frequencies. After subtraction of dc-conductivity we could analyse a second high-temperature relaxation process that is related to interface polarization induced by charge carriers trapped at the host matrix-pore interfaces. We found that, while the main effect of the oxidation on the PL appears to be a size reduction in the silicon nanocrystals that gives rise to a blue shift of the PL spectrum, its main contribution to the dielectric properties turns out to be blocking of transport channels in the host tissue and activation of hopping conductivity between silicon nanocrystals.

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...

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

Investigation on dielectric relaxation of PMMA-grafted natural rubber incorporated with LiCF3SO3

International Nuclear Information System (INIS)

Yap, K.S.; Teo, L.P.; Sim, L.N.; Majid, S.R.; Arof, A.K.

2012-01-01

Natural rubber (NR) grafted with 30 wt% poly (methyl methacrylate) (PMMA) and designated as MG30 has been added with varying amounts of LiCF 3 SO 3 . X-ray diffraction (XRD) shows the samples to be amorphous. Fourier transform infrared (FTIR) spectroscopy indicates complexation between the cation of the salt and the oxygen atom of the C=O and -COO- groups of MG30. From electrochemical impedance spectroscopy (EIS), MG30 with 30 wt% LiCF 3 SO 3 salt exhibits the highest ambient conductivity of 1.69×10 -6 S cm -1 and lowest activation energy of 0.24 eV. The dielectric behavior has been analyzed using dielectric permittivity (ε′), dissipation factor (tan δ) and dielectric modulus (M ⁎ ) of the samples. The dielectric constant of pure MG30 has been estimated to be ∼1.86.

Semiconductor-to-metallic flipping in a ZnFe{sub 2}O{sub 4}–graphene based smart nano-system: Temperature/microwave magneto-dielectric spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Ameer, Shahid, E-mail: shahidameer@scme.nust.edu.pk [School of Chemical and Materials Engineering (SCME), National University of Sciences and Technology (NUST), H-12, Islamabad (Pakistan); Gul, Iftikhar Hussain [School of Chemical and Materials Engineering (SCME), National University of Sciences and Technology (NUST), H-12, Islamabad (Pakistan); Mahmood, Nasir [Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); Mujahid, Muhammad [School of Chemical and Materials Engineering (SCME), National University of Sciences and Technology (NUST), H-12, Islamabad (Pakistan)

2015-01-15

Zn-(FeO{sub 2}){sub 2}–graphene smart nano-composites were synthesized using a novel modified solvothermal synthesis with different percentages of graphene. The structure of the nanocomposite was confirmed through X-ray diffraction, micro-Raman scattering spectroscopy, Ultraviolet–Visible spectroscopy, and Fourier transform infrared spectroscopy. The structural growth and morphological aspects were analyzed using scanning/transmission electron microscopy, revealing marvelous micro-structural features of the assembled nano-system resembling a maple leaf. To determine the composition, energy dispersive spectroscopy and X-ray photoelectron spectroscopy were used. Microwave magneto-dielectric spectroscopy revealed the improved dielectric properties of the nano-composite compared to those of the parent functional nanocrystals. Temperature gradient dielectric spectroscopy was used over the spectral range from 100 Hz to 5 MHz to reveal the phenomenological effect that the nanosystem flips from its usual semiconductor nature to a metallic nature with sensing temperature. Electrical conductivity and dielectric analysis indicated that the dielectric loss and the dielectric permittivity increased at room temperature. This extraordinary switching capability of the functionalized graphene nanosystem opens up a new dimension for engineering advanced and efficient smart composite materials. - Graphical abstract: Display Omitted - Highlights: • Zn-(FeO{sub 2}){sub 2}–graphene smart nano-composites were synthesized using a novel modified solvothermal synthesis. • The synthesized nano-system exhibits marvelous leaf like microstructure. • These nano-composites show improved magneto dielectric response. • This engineered smart nano-system shows phenomenological flipping from semiconductor like nature to metallic behavior.

Dielectric relaxation spectra of liquid crystals in relation to molecular structure

International Nuclear Information System (INIS)

Wrobel, S.

1986-07-01

The dielectric spectra obtained for some members of two homologous series, i.e. for di-alkoxyazoxybenzenes and penthyl-alkoxythiobenzoates, are discussed qualitatively on the basis of the Nordio-Rigatti-Segre diffusion model. It is additionally assumed that the molecular reorientations take place about the principal axes of the inertia tensor. The distribution of correlation times, which is strongly temperature dependent in the vicinity of the clearing point, is interpreted as being caused by fluctuations of the principal axes frame which are due to conformation changes inside the end chains. The Bauer equation is used to describe both principal molecular reorientations, i.e. the reorientations about the long and short axis, observed in liquid crystalline structure by means of dielectric relaxation methods. The energies and entropies of activation have been computed for both principal reorientations. The differences between the high frequency limit of the dielectric permittivity and the refractive index squared of liquid crystals are explained in terms of two librational motions of the molecules observed by other experimental techniques, viz. far infra-red, Raman and inelastic neutron scattering spectroscopies, and found in this work on the basis of dielectrically measured energy barriers. It has been shown qualitatively that intramolecular libratory motions greatly effect the high frequency dielectric spectrum. Finally, molecular motions in liquid crystals are divided into two types: coherent and incoherent. 127 refs., 56 figs., 17 tabs. (author)

Infrared optical responses of wurtzite In{sub x}Ga{sub 1−x}N thin films with porous surface morphology

Energy Technology Data Exchange (ETDEWEB)

Yew, P., E-mail: paulinevcu@hotmail.com [Institute of Nano-Optoelectronics Research and Technology (INOR), Universiti Sains Malaysia, 11800 Minden, Penang (Malaysia); School of Physics, Universiti Sains Malaysia, 11800 Minden, Penang (Malaysia); Lee, S.C. [School of Physics, Universiti Sains Malaysia, 11800 Minden, Penang (Malaysia); Centre of Excellence for Pre-University Studies, INTI International College Penang, Laureate International University, 1-Z, Lebuh Bukit Jambul, 11900 Penang (Malaysia); Ng, S.S. [Institute of Nano-Optoelectronics Research and Technology (INOR), Universiti Sains Malaysia, 11800 Minden, Penang (Malaysia); Hassan, H. Abu [School of Physics, Universiti Sains Malaysia, 11800 Minden, Penang (Malaysia); Chen, W.L. [Department of Electronic Engineering, National Changhua University of Education, 500, Taiwan, ROC (China); Osipowicz, T.; Ren, M.Q. [Centre for Ion Beam Applications (CIBA), Department of Physics, National University of Singapore, Singapore 119260 (Singapore)

2016-03-31

Room temperature infrared (IR) optical responses of wurtzite indium gallium nitride (In{sub x}Ga{sub 1−x}N) in the composition range of 0.174 ≤ x ≤ 0.883 were investigated by the polarized IR reflectance spectroscopy. Analyses of the amplitudes of oscillation fringes in the non-reststrahlen region revealed that the high frequency dielectric constants of the samples were unusually smaller than the values predicted from the Clausius–Mossotti relation. This odd behavior was attributed to the porous surface morphology of the In{sub x}Ga{sub 1−x}N samples. The E{sub 1} optical phonon modes of the In{sub x}Ga{sub 1−x}N were deduced from the composition dependent reststrahlen features. The obtained values were compared to those calculated through the modified random element iso-displacement (MREI) model. The deviation between the measured data and the MREI model prediction were explained in detail from the aspects of strain, thermal expansion and anharmonic phonon-coupling. Finally, it was found that the large discrepancy of the E{sub 1}(LO) mode is mainly attributed to the effects of the longitudinal phonon–plasmon coupling. - Highlights: • Composition dependence of E{sub 1} modes of In{sub x}Ga{sub 1−x}N alloys (x = 0.174 to 0.883) • Dependence of porous morphology on infrared (IR) optical properties • Longitudinal phonon–plasmon coupling obscures determination of E{sub 1}(LO) mode.

Electroactive Phase Induced Bi4Ti3O12-Poly(Vinylidene Difluoride) Composites with Improved Dielectric Properties

Science.gov (United States)

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

2015-10-01

Lead-free ceramic-polymer composite films containing Bi4Ti3O12 (BIT) nanocrystals as the active phase and poly(vinylidene difluoride) as the passive matrix were synthesized by spin coating. The films' structural, morphological, and dielectric properties were systemically investigated by varying the weight fraction of BIT. Formation of electroactive β and γ phases were strongly affected by the presence of BIT nanocrystals. Analysis was performed by Fourier-transform infrared and Raman spectroscopy. Morphological studies confirmed the homogeneous dispersion of BIT particles within the polymer matrix. The composite films had dielectric constants as high as 52.8 and low dielectric loss of 0.1 at 100 Hz when the BIT content was 10 wt.%. We suggest that the enhanced electroactive phase content of the polymer matrix and interfacial polarization may contribute to the improved dielectric performance of these composite films. Dielectric modulus analysis was performed to enable understanding of the dielectric relaxation process. Non-Debye-type relaxation behavior was observed for the composite films at high temperature.

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 property of NiTiO3 doped substituted ortho-chloropolyaniline composites

Directory of Open Access Journals (Sweden)

Mohana Lakshmi

2013-11-01

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

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.

Optical response of thin amorphous films to infrared radiation

Science.gov (United States)

Orosco, J.; Coimbra, C. F. M.

2018-03-01

We briefly review the electrical-optical response of materials to radiative forcing within the formalism of the Kramers-Kronig relations. A commensurate set of criteria is described that must be met by any frequency-domain model representing the time-domain response of a real (i.e., physically possible) material. The criteria are applied to the Brendel-Bormann (BB) oscillator, a model that was originally introduced for its fidelity at reproducing the non-Lorentzian peak broadening experimentally observed in the infrared absorption by thin amorphous films but has since been used for many other common materials. We show that the BB model fails to satisfy the established physical criteria. Taking an alternative approach to the model derivation, a physically consistent model is proposed. This model provides the appropriate line-shape broadening for modeling the infrared optical response of thin amorphous films while adhering strictly to the Kramers-Kronig criteria. Experimental data for amorphous alumina (Al2O3 ) and amorphous quartz silica (SiO2) are used to obtain model parametrizations for both the noncausal BB model and the proposed causal model. The proposed model satisfies consistency criteria required by the underlying physics and reproduces the experimental data with better fidelity (and often with fewer parameters) than previously proposed permittivity models.

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.

Optical Cladding Waveguides in Dielectric Crystals Produced by Femtosecond Laser Inscription

Directory of Open Access Journals (Sweden)

Chen Feng

2013-11-01

Full Text Available In this work, the recent progress of our research on optical cladding waveguides in dielectric crystals produced by femtosecond laser inscription has been overviewed. With different scales at cross sections, the cladding waveguides support guidance from single mode to highly multi-modes, and work for wavelength till mid-infrared regimes. Applications of the fabricated cladding structures as new integrated light sources are introduced.

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)

Infrared neural stimulation (INS) inhibits electrically evoked neural responses in the deaf white cat

Science.gov (United States)

Richter, Claus-Peter; Rajguru, Suhrud M.; Robinson, Alan; Young, Hunter K.

2014-03-01

Infrared neural stimulation (INS) has been used in the past to evoke neural activity from hearing and partially deaf animals. All the responses were excitatory. In Aplysia californica, Duke and coworkers demonstrated that INS also inhibits neural responses [1], which similar observations were made in the vestibular system [2, 3]. In deaf white cats that have cochleae with largely reduced spiral ganglion neuron counts and a significant degeneration of the organ of Corti, no cochlear compound action potentials could be observed during INS alone. However, the combined electrical and optical stimulation demonstrated inhibitory responses during irradiation with infrared light.

Preparation and structure of porous dielectrics by plasma enhanced chemical vapor deposition

International Nuclear Information System (INIS)

Gates, S. M.; Neumayer, D. A.; Sherwood, M. H.; Grill, A.; Wang, X.; Sankarapandian, M.

2007-01-01

The preparation of ultralow dielectric constant porous silicon, carbon, oxygen, hydrogen alloy dielectrics, called 'pSiCOH', using a production 200 mm plasma enhanced chemical vapor deposition tool and a thermal treatment is reported here. The effect of deposition temperature on the pSiCOH film is examined using Fourier transform infrared (FTIR) spectroscopy, dielectric constant (k), and film shrinkage measurements. For all deposition temperatures, carbon in the final porous film is shown to be predominantly Si-CH 3 species, and lower k is shown to correlate with increased concentration of Si-CH 3 . NMR and FTIR spectroscopies clearly detect the loss of a removable, unstable, hydrocarbon (CH x ) phase during the thermal treatment. Also detected are increased cross-linking of the Si-O skeleton, and concentration changes for three distinct structures of carbon. In the as deposited films, deposition temperature also affects the hydrocarbon (CH x ) content and the presence of C=O and C=C functional groups

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...

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...

Near-Infrared Trigged Stimulus-Responsive Photonic Crystals with Hierarchical Structures.

Science.gov (United States)

Lu, Tao; Pan, Hui; Ma, Jun; Li, Yao; Zhu, Shenmin; Zhang, Di

2017-10-04

Stimuli-responsive photonic crystals (PCs) trigged by light would provide a novel intuitive and quantitative method for noninvasive detection. Inspired by the flame-detecting aptitude of fire beetles and the hierarchical photonic structures of butterfly wings, we herein developed near-infrared stimuli-responsive PCs through coupling photothermal Fe 3 O 4 nanoparticles with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM), with hierarchical photonic structured butterfly wing scales as the template. The nanoparticles within 10 s transferred near-infrared radiation into heat that triggered the phase transition of PNIPAM; this almost immediately posed an anticipated effect on the PNIPAM refractive index and resulted in a composite spectrum change of ∼26 nm, leading to the direct visual readout. It is noteworthy that the whole process is durable and stable mainly owing to the chemical bonding formed between PNIPAM and the biotemplate. We envision that this biologically inspired approach could be utilized in a broad range of applications and would have a great impact on various monitoring processes and medical sensing.

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...

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.

Inter-atomic bonding and dielectric polarization in Gd{sup 3+} incorporated Co-Zn ferrite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Pawar, R.A. [Department of Physics, P.V.P. Arts, Commerce and Science College, Pravaranagar, MS (India); Desai, S.S. [Materials Research Laboratory, Shrikrishna Mahavidyalaya, Gunjoti 413613, MS (India); Patange, S.M., E-mail: drsmpatange@rediffmail.com [Materials Research Laboratory, Shrikrishna Mahavidyalaya, Gunjoti 413613, MS (India); Jadhav, S.S. [Department of Physics, Dnyanopasak Shikshan Mandal' s Arts, Commerce and Science College, Jintur 431509, MS (India); Jadhav, K.M. [Department of Physics, Dr Babasaheb Ambedkar Marathwada University, Aurangabad 431001, MS (India)

2017-04-01

A series of ferrite with a chemical composition Co{sub 0.7}Zn{sub 0.3}Gd{sub x}Fe{sub 2−x}O{sub 4} (where x=0.0 to x=0.1) were prepared by sol-gel auto-combustion method. X-ray diffraction pattern were used to determine the crystal structure and phase formation of the prepared samples. Scanning electron microscopy is used to study the surface morphology of the prepared samples. Elastic properties were determined from the infrared spectroscopy. Debye temperature, wave velocities, elastic constants found to increase with the increase in Gd{sup 3+} substitution. Dielectric properties such as dielectric constant and dielectric loss were studied as a function of Gd{sup 3+} substitution and frequency. Dielectric constant decreased with the increase in frequency and Gd{sup 3+} substitution. Behavior of dielectric properties was explained on the basis of Maxwell-Wagner interfacial polarization which in accordance with Koops phenomenological theory. Real and imaginary part of impedance was studied as a function of resistance and Gd{sup 3+} substitution. The behavior of impedance is systematically discussed on the basis of resistance-capacitance circuit.

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 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

The influence of neutron-irradiation at low temperatures on the dielectric parameters of 3C-SiC

Energy Technology Data Exchange (ETDEWEB)

Engelbrecht, J.A.A., E-mail: Japie.Engelbrecht@nmmu.ac.za [Physics Department, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Deyzel, G.; Minnaar, E.G.; Goosen, W.E. [Physics Department, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Rooyen, I.J. van [Fuel Performance and Design Department, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-6188 (United States)

2014-04-15

3C-SiC wafers were irradiated with neutrons of various fluences and at low (200–400 °C) irradiation temperatures. Fourier transform infrared (FTIR) reflectance spectra were obtained for the samples, and the spectra used to extract the dielectric parameters for each specimen, using statistical curve-fitting procedures. Analysis of all data revealed trends in reflectance peak heights as well as in the dielectric parameters. The surface roughness of the irradiated samples was measured by atomic force spectroscopy (AFM) and certain trends could be ascribed to surface roughness.

The influence of neutron-irradiation at low temperatures on the dielectric parameters of 3C-SiC

International Nuclear Information System (INIS)

Engelbrecht, J.A.A.; Deyzel, G.; Minnaar, E.G.; Goosen, W.E.; Rooyen, I.J. van

2014-01-01

3C-SiC wafers were irradiated with neutrons of various fluences and at low (200–400 °C) irradiation temperatures. Fourier transform infrared (FTIR) reflectance spectra were obtained for the samples, and the spectra used to extract the dielectric parameters for each specimen, using statistical curve-fitting procedures. Analysis of all data revealed trends in reflectance peak heights as well as in the dielectric parameters. The surface roughness of the irradiated samples was measured by atomic force spectroscopy (AFM) and certain trends could be ascribed to surface roughness.

Dielectric, thermal and mechanical properties of ADP doped PVA composites

Science.gov (United States)

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

2015-06-01

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

Structural, morphological and dielectric studies of zirconium substituted CoFe2O4 nanoparticles

Directory of Open Access Journals (Sweden)

S. Anand

2017-12-01

Full Text Available In this work, the influence of zirconium substitution in cubic spinel nanocrystalline CoFe2O4 on the structural, morphological and dielectric properties are reported. Zirconium substituted cobalt ferrite Co1-xZrxFe2O4 (x = 0.7 nanoparticles were synthesized by sol-gel route. The structural and morphological investigations using powder X-ray diffraction and high resolution scanning electron microscope (HRSEM analysis are reported. Scherrer plot, Williamson–Hall analysis and Size-strain plot method were used to calculate the crystallite size and lattice strain of the samples. High purity chemical composition of the sample was confirmed by energy dispersive X-ray analysis. The atoms vibration modes of as synthesized nanoparticles were recorded using Fourier transform infrared (FTIR spectrometer in the range of 4000–400 cm-1. The temperature-dependent dielectric properties of zirconium substituted cobalt ferrite nanoparticles were also carried out. Relative dielectric permittivity, loss tangent and AC conductivity were measured in the frequency range 50 Hz to 5 MHz at temperatures between 323 K and 473 K. The dielectric constant and dielectric loss values of the sample decreased with increasing in the frequency of the applied signal.

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.

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.

Impact of dielectric parameters on the reflectivity of 3C–SiC wafers with a rough surface morphology in the reststrahlen region

International Nuclear Information System (INIS)

Engelbrecht, J.A.A.; Janzén, E.; Henry, A.; Rooyen, I.J. van

2014-01-01

A layer-on-substrate model is used to obtain the infrared reflectance for 3C–SiC with a rough surface morphology. The effect of varying dielectric parameters of the “damaged layer” on the observed reflectivity of the 3C–SiC in the reststrahlen region is assessed. Different simulated reflectance spectra are obtained to those if the dielectric parameters of the “substrate” were varied. Most notable changes in the shape of the simulated reststrahlen peak are observed for changes in the high frequency dielectric constant, the phonon damping constant, the phonon frequencies and “thickness” of damaged surface layer.

Impact of dielectric parameters on the reflectivity of 3C–SiC wafers with a rough surface morphology in the reststrahlen region

Energy Technology Data Exchange (ETDEWEB)

Engelbrecht, J.A.A., E-mail: Japie.Engelbrecht@nmmu.ac.za [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); Janzén, E.; Henry, A. [Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping (Sweden); Rooyen, I.J. van [Fuel Performance and Design Department, Idaho National Laboratory, PO Box 1625, Idaho Falls, ID 83415-6188 (United States)

2014-04-15

A layer-on-substrate model is used to obtain the infrared reflectance for 3C–SiC with a rough surface morphology. The effect of varying dielectric parameters of the “damaged layer” on the observed reflectivity of the 3C–SiC in the reststrahlen region is assessed. Different simulated reflectance spectra are obtained to those if the dielectric parameters of the “substrate” were varied. Most notable changes in the shape of the simulated reststrahlen peak are observed for changes in the high frequency dielectric constant, the phonon damping constant, the phonon frequencies and “thickness” of damaged surface layer.

Growth and Dielectric Properties of Ta-Doped La2Ti2O7 Single Crystals

Directory of Open Access Journals (Sweden)

Hui Wang

2018-02-01

Full Text Available High-quality Ta-doped La2Ti2O7 (Ta-LTO single crystal of about 40 mm in length and 5 mm in diameter was successfully prepared by the optical floating zone method. An X-ray rocking curve reveals that the crystal of LTO has excellent crystalline quality. As-grown crystals were transparent after annealing in air and the transmittance is up to 76% in the visible and near-infrared region. X-ray diffraction showed that this compound possessed a monoclinic structure with P21 space group. The dielectric properties were investigated as functions of temperature (0~300 °C and frequency (102 Hz~105 Hz. Dielectric spectra indicated an increase in the room-temperature dielectric constant accompanied by a drop in the loss tangent as a result of the Ta doping. One relaxation was observed in the spectra of electric modulus, which was ascribed to be related to the oxygen vacancy. The dielectric relaxation with activation energy of 1.16 eV is found to be the polaron hopping caused by the oxygen vacancies.

Investigation on dielectric relaxation of PMMA-grafted natural rubber incorporated with LiCF{sub 3}SO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Yap, K.S.; Teo, L.P.; Sim, L.N.; Majid, S.R. [Centre for Ionics University of Malaya, Physics Department, University of Malaya, 50603 Kuala Lumpur (Malaysia); Arof, A.K., E-mail: akarof@um.edu.my [Centre for Ionics University of Malaya, Physics Department, University of Malaya, 50603 Kuala Lumpur (Malaysia)

2012-07-01

Natural rubber (NR) grafted with 30 wt% poly (methyl methacrylate) (PMMA) and designated as MG30 has been added with varying amounts of LiCF{sub 3}SO{sub 3}. X-ray diffraction (XRD) shows the samples to be amorphous. Fourier transform infrared (FTIR) spectroscopy indicates complexation between the cation of the salt and the oxygen atom of the C=O and -COO- groups of MG30. From electrochemical impedance spectroscopy (EIS), MG30 with 30 wt% LiCF{sub 3}SO{sub 3} salt exhibits the highest ambient conductivity of 1.69 Multiplication-Sign 10{sup -6} S cm{sup -1} and lowest activation energy of 0.24 eV. The dielectric behavior has been analyzed using dielectric permittivity ({epsilon} Prime), dissipation factor (tan {delta}) and dielectric modulus (M{sup Low-Asterisk }) of the samples. The dielectric constant of pure MG30 has been estimated to be {approx}1.86.

Optimal hemodynamic response model for functional near-infrared spectroscopy

Directory of Open Access Journals (Sweden)

Muhammad Ahmad Kamran

2015-06-01

Full Text Available Functional near-infrared spectroscopy (fNIRS is an emerging non-invasive brain imaging technique and measures brain activities by means of near-infrared light of 650-950 nm wavelengths. The cortical hemodynamic response (HR differs in attributes at different brain regions and on repetition of trials, even if the experimental paradigm is kept exactly the same. Therefore, an HR model that can estimate such variations in the response is the objective of this research. The canonical hemodynamic response function (cHRF is modeled by using two Gamma functions with six unknown parameters. The HRF model is supposed to be linear combination of HRF, baseline and physiological noises (amplitudes and frequencies of physiological noises are supposed to be unknown. An objective function is developed as a square of the residuals with constraints on twelve free parameters. The formulated problem is solved by using an iterative optimization algorithm to estimate the unknown parameters in the model. Inter-subject variations in HRF and physiological noises have been estimated for better cortical functional maps. The accuracy of the algorithm has been verified using ten real and fifteen simulated data sets. Ten healthy subjects participated in the experiment and their HRF for finger-tapping tasks have been estimated and analyzed. The statistical significance of the estimated activity strength parameters has been verified by employing statistical analysis, i.e., (t-value >tcritical and p-value < 0.05.

Optimal hemodynamic response model for functional near-infrared spectroscopy.

Science.gov (United States)

Kamran, Muhammad A; Jeong, Myung Yung; Mannan, Malik M N

2015-01-01

Functional near-infrared spectroscopy (fNIRS) is an emerging non-invasive brain imaging technique and measures brain activities by means of near-infrared light of 650-950 nm wavelengths. The cortical hemodynamic response (HR) differs in attributes at different brain regions and on repetition of trials, even if the experimental paradigm is kept exactly the same. Therefore, an HR model that can estimate such variations in the response is the objective of this research. The canonical hemodynamic response function (cHRF) is modeled by two Gamma functions with six unknown parameters (four of them to model the shape and other two to scale and baseline respectively). The HRF model is supposed to be a linear combination of HRF, baseline, and physiological noises (amplitudes and frequencies of physiological noises are supposed to be unknown). An objective function is developed as a square of the residuals with constraints on 12 free parameters. The formulated problem is solved by using an iterative optimization algorithm to estimate the unknown parameters in the model. Inter-subject variations in HRF and physiological noises have been estimated for better cortical functional maps. The accuracy of the algorithm has been verified using 10 real and 15 simulated data sets. Ten healthy subjects participated in the experiment and their HRF for finger-tapping tasks have been estimated and analyzed. The statistical significance of the estimated activity strength parameters has been verified by employing statistical analysis (i.e., t-value > t critical and p-value < 0.05).

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.

Sunlight-driven eco-friendly smart curtain based on infrared responsive graphene oxide-polymer photoactuators.

Science.gov (United States)

Leeladhar; Raturi, Parul; Singh, J P

2018-02-27

Photomechanical actuation is the conversion of light energy into mechanical energy through some smart materials. Infrared-responsive smart materials have become an emerging field of research due to easy availability and eco-friendly nature of their stimulus in the form of sunlight, which contains about 50% of near-infrared(nIR) making these materials useful at macro-scale photoactuator applications. Here, we demonstrate fabrication of highly versatile nIR triggered photoactuators based on graphene oxide/polycarbonate bilayers that offers fast, low-cost fabrication, large deflection, reversible actuation and wavelength-selective response. The photoactuators are realized by vacuum filtration of graphene oxide/water dispersion through polycarbonate membrane resulting graphene oxide/polymer bilayer structure. The photoactuation response was measured in the form of deflection from equilibrium position as a result of infrared-irradiation. The deflection is caused by the generated thermal stress at the interface of bilayers due to mismatch of thermal expansion coefficient as a results of nIR absorption by graphene oxide and subsequent temperature rise. A maximum deflection of 12 mm (circular-shaped structure with diameter 28 mm) with corresponding bending curvature of 0.33 cm -1 was shown by this photoactuator for illumination intensity of 106 mW/cm 2 . Few applications of these photoactuators such as sunlight-driven smart curtain, infrared actuated curtain and self-folding box are also demonstrated.

Dielectric, electrical and infrared studies of γ-Fe2O3 prepared by ...

Indian Academy of Sciences (India)

Unknown

Murthy V R K 1990 Low frequency dielectric properties of ferrites (eds) V R K Murthy and B Viswanatham (New. Delhi: Narosa Publication) Ch. IV, ed. 1. Murthy V R K and Sobhanadri J 1976 J. Phys. Status Solidi. (a)36k 133. Rahman M M and Venkataraman A 2002 J. Therm. Anal. Cal. 68 91. Rane K S, Verenkar V M S and ...

Critical coupling using the hexagonal boron nitride crystals in the mid-infrared range

Energy Technology Data Exchange (ETDEWEB)

Wu, Jipeng; Wang, Hengliang; Wen, Shuangchun [Key Laboratory for Micro-/Nano-Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410082 (China); Jiang, Leyong; Guo, Jun; Dai, Xiaoyu [SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Xiang, Yuanjiang, E-mail: xiangyuanjiang@126.com [Key Laboratory for Micro-/Nano-Optoelectronic Devices of Ministry of Education, School of Physics and Electronics, Hunan University, Changsha 410082 (China); SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China)

2016-05-28

We theoretically demonstrate the perfect absorption phenomena in the hexagonal boron nitride (hBN) crystals in the mid-infrared wavelength ranges by means of critical coupling with a one-dimensional photonic crystal spaced by the air. Different from the polymer absorbing layer composed by a metal-dielectric composite film, the hyperbolic dispersion characteristics of hBN can meet the condition of critical coupling and achieve the total absorption in the mid-infrared wavelength ranges. However, the critical coupling phenomenon can only appear in the hBN crystals with the type II dispersion. Moreover, we discuss the influence of the thickness of hBN, the incident angle, and the thickness and permittivity of the space dielectric on the total absorption. Ultimately, the conditions for absorption enhancement and the optimization methods of perfect absorption are proposed, and the design rules for a totally absorbing system under the different conditions are achieved.

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.

Dielectric dispersion, relaxation dynamics and thermodynamic studies of Beta-Alanine in aqueous solutions using picoseconds time domain reflectometry

Science.gov (United States)

Vinoth, K.; Ganesh, T.; Senthilkumar, P.; Sylvester, M. Maria; Karunakaran, D. J. S. Anand; Hudge, Praveen; Kumbharkhane, A. C.

2017-09-01

The aqueous solution of beta-alanine characterised and studied by their dispersive dielectric properties and relaxation process in the frequency domain of 10×106 Hz to 30×109 Hz with varying concentration in mole fractions and temperatures. The molecular interaction and dielectric parameters are discussed in terms of counter-ion concentration theory. The static permittivity (ε0), high frequency dielectric permittivity (ε∞) and excess dielectric parameters are accomplished by frequency depended physical properties and relaxation time (τ). Molecular orientation, ordering and correlation factors are reported as confirmation of intermolecular interactions. Ionic conductivity and thermo dynamical properties are concluded with the behaviour of the mixture constituents. Solute-solvent, solute-solute interaction, structure making and breaking abilities of the solute in aqueous medium are interpreted. Fourier Transform Infrared (FTIR) spectra of beta- alanine single crystal and liquid state have been studied. The 13C Nuclear Magnetic Resonance (NMR) spectral studies give the signature for resonating frequencies and chemical shifts of beta-alanine.

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...

Far-infrared ferroelectric soft mode spectroscopy on thin films

Czech Academy of Sciences Publication Activity Database

Petzelt, Jan; Ostapchuk, Tetyana

2001-01-01

Roč. 249, 1-2 (2001), s. 81-88 ISSN 0015-0193 R&D Projects: GA ČR GA202/98/1282; GA AV ČR IAA1010918; GA MŠk OC 514.10 Institutional research plan: CEZ:AV0Z1010914 Keywords : far-infrared spectroscopy * soft mode * dielectric spectra * permitivity Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.471, year: 2001

All-dielectric resonant cavity-enabled metals with broadband optical transparency

Science.gov (United States)

Liu, Zhengqi; Zhang, Houjiao; Liu, Xiaoshan; Pan, Pingping; Liu, Yi; Tang, Li; Liu, Guiqiang

2017-06-01

Metal films with broadband optical transparency are desirable in many optoelectronic devices, such as displays, smart windows, light-emitting diodes and infrared detectors. As bare metal is opaque to light, this issue of transparency attracts great scientific interest. In this work, we proposed and demonstrated a feasible and universal approach for achieving broadband optical transparent (BOT) metals by utilizing all-dielectric resonant cavities. Resonant dielectrics provide optical cavity modes and couple strongly with the surface plasmons of the metal film, and therefore produce a broadband near-unity optical transparent window. The relative enhancement factor (EF) of light transmission exceeds 3400% in comparison with that of pure metal film. Moreover, the transparent metal motif can be realized by other common metals including gold (Au), silver (Ag) and copper (Cu). These optical features together with the fully retained electric and mechanical properties of a natural metal suggest that it will have wide applications in optoelectronic devices.

An omnidirectional retroreflector based on the transmutation of dielectric singularities.

Science.gov (United States)

Ma, Yun Gui; Ong, C K; Tyc, Tomás; Leonhardt, Ulf

2009-08-01

Transformation optics is a concept used in some metamaterials to guide light on a predetermined path. In this approach, the materials implement coordinate transformations on electromagnetic waves to create the illusion that the waves are propagating through a virtual space. Transforming space by appropriately designed materials makes devices possible that have been deemed impossible. In particular, transformation optics has led to the demonstration of invisibility cloaking for microwaves, surface plasmons and infrared light. Here, on the basis of transformation optics, we implement a microwave device that would normally require a dielectric singularity, an infinity in the refractive index. To fabricate such a device, we transmute a dielectric singularity in virtual space into a mere topological defect in a real metamaterial. In particular, we demonstrate an omnidirectional retroreflector, a device for faithfully reflecting images and for creating high visibility from all directions. Our method is robust, potentially broadband and could also be applied to visible light using similar techniques.

Dielectric relaxations above room temperature in DMPU derived polyaniline film

International Nuclear Information System (INIS)

Mallya, Ashwini N.; Yashavanth Kumar, G.S.; Ranjan, Rajeev; Ramamurthy, Praveen C.

2012-01-01

Dielectric measurements carried out on drop casted from solution of emeraldine base form of polyaniline films in the temperature range 30-300 °C revealed occurrence of two maxima in the loss tangent as a function of temperature. The activation energies corresponding to these two relaxation processes were found to be ∼0.5 eV and ∼1.5 eV. The occurrence of one relaxation peak in the dispersion curve of the imaginary part of the electric modulus suggests the absence of microphase separation in the film. Thermogravimetric analysis and infrared spectroscopic measurements showed that the films retained its integrity up to 300 °C. The dielectric relaxation at higher temperatures with large activation energy of 1.5 eV is attributed to increase in the barrier potential due to decrease in the polymer conjugation as a result of wide amplitude motion of the chain segments well above the glass transition temperature.

Dielectric relaxations above room temperature in DMPU derived polyaniline film

Energy Technology Data Exchange (ETDEWEB)

Mallya, Ashwini N.; Yashavanth Kumar, G.S.; Ranjan, Rajeev [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India); Ramamurthy, Praveen C., E-mail: onegroupb203@gmail.com [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India)

2012-09-15

Dielectric measurements carried out on drop casted from solution of emeraldine base form of polyaniline films in the temperature range 30-300 Degree-Sign C revealed occurrence of two maxima in the loss tangent as a function of temperature. The activation energies corresponding to these two relaxation processes were found to be {approx}0.5 eV and {approx}1.5 eV. The occurrence of one relaxation peak in the dispersion curve of the imaginary part of the electric modulus suggests the absence of microphase separation in the film. Thermogravimetric analysis and infrared spectroscopic measurements showed that the films retained its integrity up to 300 Degree-Sign C. The dielectric relaxation at higher temperatures with large activation energy of 1.5 eV is attributed to increase in the barrier potential due to decrease in the polymer conjugation as a result of wide amplitude motion of the chain segments well above the glass transition temperature.

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

Far-infrared vibrational modes of DNA components studied by terahertz time-domain spectroscopy

International Nuclear Information System (INIS)

Fischer, B M; Walther, M; Jepsen, P Uhd

2002-01-01

The far-infrared dielectric function of a wide range of organic molecules is dominated by vibrations involving a substantial fraction of the atoms forming the molecule and motion associated with intermolecular hydrogen bond vibrations. Due to their collective nature such modes are highly sensitive to the intra- and intermolecular structure and thus provide a unique fingerprint of the conformational state of the molecule and effects of its environment. We demonstrate the use of terahertz time-domain spectroscopy (THz-TDS) for recording the far-infrared (0.5-4.0 THz) dielectric function of the four nucleobases and corresponding nucleosides forming the building blocks of deoxyribose nucleic acid (DNA). We observe numerous distinct spectral features with large differences between the molecules in both frequency-dependent absorption coefficient and index of refraction. Assisted by results from density-functional calculations we interpret the origin of the observed resonances as vibrations of hydrogen bonds between the molecules

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.

Mid-infrared plasmonic resonances exploiting heavily-doped Ge on Si

Science.gov (United States)

Biagioni, P.; Sakat, E.; Baldassarre, L.; Calandrini, E.; Samarelli, A.; Gallacher, K.; Frigerio, J.; Isella, G.; Paul, D. J.; Ortolani, M.

2015-03-01

We address the behavior of mid-infrared localized plasmon resonances in elongated germanium antennas integrated on silicon substrates. Calculations based on Mie theory and on the experimentally retrieved dielectric constant allow us to study the tunability and the figures of merit of plasmon resonances in heavily-doped germanium and to preliminarily compare them with those of the most established plasmonic material, gold.

Moisture content determination in solid biofuels by dielectric and NIR reflection methods

Energy Technology Data Exchange (ETDEWEB)

Jensen, Peter Daugbjerg; Morsing, Merete [Department of Forest and Landscape, The Royal Veterinary and Agricultural University, Rolighedsvej 23, DK-1958 Frederiksberg C (Denmark); Hartmann, Hans; Boehm, Thorsten [Technologie- und Foerderzentrum fuer Nachwachsende Rohstoffe (TFZ), Schulgasse 18, D-94315 Straubing (Germany); Temmerman, Michael; Rabier, Fabienne [Departement Genie Rural, Chee de Namur 146, B-5030 Gembloux (Belgium)

2006-11-15

One near infrared (NIR) reflectance and five dielectric moisture meters were tested for their capability of measuring moisture content (MC) in solid biofuels. Ninety-eight samples were tested at up to eight moisture levels covering the MC range from fresh fuel to approximately 10% MC (w.b.). The fuel types ranged from typical solid biofuels such as coniferous and deciduous wood chips over short rotation coppice (SRC) to sunflower seed and olive stones. The most promising calibrations were obtained with the NIR reflection method and two dielectric devices where the sample is placed in a container integrated in the device. The calibration equations developed show that there is a profound influence from both laboratory and fuel type. It is suggested that individual calibrations that are based on the specific fuel types used at the individual heating plant could be applied. (author)

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...

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...

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.

Physiological response of Arundo donax to cadmium stress by Fourier transform infrared spectroscopy.

Science.gov (United States)

Yu, Shunhui; Sheng, Li; Zhang, Chunyan; Deng, Hongping

2018-06-05

The present paper deals with the physiological response of the changes in chemical contents of the root, stem and leaf of Arundo donax seedlings stressed by excess cadmium using Fourier transform infrared spectroscopy technique, cadmium accumulation in plant by atomic absorption spectroscopy were tested after different concentrations cadmium stress. The results showed that low cadmium concentrations (Fourier transform infrared spectroscopy technique for the non-invasive and rapid monitoring of the plants stressed with heavy metals, Arundo donax is suitable for phytoremediation of cadmium -contaminated wetland. Copyright © 2018 Elsevier B.V. All rights reserved.

Stimulated emission of surface plasmon polaritons by lead-sulphide quantum dots at near infra-red wavelengths

DEFF Research Database (Denmark)

Radko, Ilya P.; Nielsen, Michael Grøndahl; Albrektsen, Ole

2010-01-01

Amplification of surface plasmon polaritons (SPPs) in planar metal-dielectric structure through stimulated emission is investigated using leakage-radiation microscopy configuration. The gain medium is a thin polymethylmethacrylate layer doped with lead-sulphide nanocrystals emitting at near-infrared...

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.

Theoretical study of the attenuation of a gaussian beam penetrating into a dielectric circular wave guide

International Nuclear Information System (INIS)

Crenn, J.P.

1981-07-01

It is proposed to draw up an approximate formula directly giving the attenuation of a gaussian beam penetrating into a superdimensioned dielectric circular wave guide. This formula is derived from optical laws, i.e. Fresnel's formulae of the reflexion of a wave on a dielectric to which a correcting term due to diffraction has been added. The results given by this formula are compared with the existing results, based on the breakdown of a gaussian beam into propagation modes, thereby enabling their validity and the field of use to be checked. An application is then made to the wave guides that will be employed in the infrared interferometer fitted in JET [fr

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)

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.

The relationship between chemical structure and dielectric properties of plasma-enhanced chemical vapor deposited polymer thin films

Energy Technology Data Exchange (ETDEWEB)

Jiang Hao [Materials Sci and Tech Applications, LLC, 409 Maple Springs Drive, Dayton OH 45458 (United States)]. E-mail: hao.jiang@wpafb.af.mil; Hong Lianggou [Materials Sci and Tech Applications, LLC, 409 Maple Springs Drive, Dayton OH 45458 (United States); Venkatasubramanian, N. [Research Institute, University of Dayton, 300 College Park, Dayton, OH 45469-0168 (United States); Grant, John T. [Research Institute, University of Dayton, 300 College Park, Dayton, OH 45469-0168 (United States); Eyink, Kurt [Air Force Research Laboratory, Materials Directorate, 3005 Hobson Way, Wright-Patterson Air Force Base, OH 45433-7707 (United States); Wiacek, Kevin [Air Force Research Laboratory, Propulsion Directorate, 1950 Fifth Street, Wright-Patterson Air Force Base, OH 45433-7251 (United States); Fries-Carr, Sandra [Air Force Research Laboratory, Propulsion Directorate, 1950 Fifth Street, Wright-Patterson Air Force Base, OH 45433-7251 (United States); Enlow, Jesse [Air Force Research Laboratory, Materials Directorate, 3005 Hobson Way, Wright-Patterson Air Force Base, OH 45433-7707 (United States); Bunning, Timothy J. [Air Force Research Laboratory, Materials Directorate, 3005 Hobson Way, Wright-Patterson Air Force Base, OH 45433-7707 (United States)

2007-02-26

Polymer dielectric films fabricated by plasma enhanced chemical vapor deposition (PECVD) have unique properties due to their dense crosslinked bulk structure. These spatially uniform films exhibit good adhesion to a variety of substrates, excellent chemical inertness, high thermal resistance, and are formed from an inexpensive, solvent-free, room temperature process. In this work, we studied the dielectric properties of plasma polymerized (PP) carbon-based polymer thin films prepared from two precursors, benzene and octafluorocyclobutane. Two different monomer feed locations, directly in the plasma zone or in the downstream region (DS) and two different pressures, 80 Pa (high pressure) or 6.7 Pa (low pressure), were used. The chemical structure of the PECVD films was examined by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. The dielectric constant ({epsilon} {sub r}) and dielectric loss (tan {delta}) of the films were investigated over a range of frequencies up to 1 MHz and the dielectric strength (breakdown voltage) (F {sub b}) was characterized by the current-voltage method. Spectroscopic ellipsometry was performed to determine the film thickness and refractive index. Good dielectric properties were exhibited, as PP-benzene films formed in the high pressure, DS region showed a F{sub b} of 610 V/{mu}m, an {epsilon} {sub r} of 3.07, and a tan {delta} of 7.0 x 10{sup -3} at 1 kHz. The PECVD processing pressure has a significant effect on final film structure and the film's physical density has a strong impact on dielectric breakdown strength. Also noted was that the residual oxygen content in the PP-benzene films significantly affected the frequency dependences of the dielectric constant and loss.

The relationship between chemical structure and dielectric properties of plasma-enhanced chemical vapor deposited polymer thin films

International Nuclear Information System (INIS)

Jiang Hao; Hong Lianggou; Venkatasubramanian, N.; Grant, John T.; Eyink, Kurt; Wiacek, Kevin; Fries-Carr, Sandra; Enlow, Jesse; Bunning, Timothy J.

2007-01-01

Polymer dielectric films fabricated by plasma enhanced chemical vapor deposition (PECVD) have unique properties due to their dense crosslinked bulk structure. These spatially uniform films exhibit good adhesion to a variety of substrates, excellent chemical inertness, high thermal resistance, and are formed from an inexpensive, solvent-free, room temperature process. In this work, we studied the dielectric properties of plasma polymerized (PP) carbon-based polymer thin films prepared from two precursors, benzene and octafluorocyclobutane. Two different monomer feed locations, directly in the plasma zone or in the downstream region (DS) and two different pressures, 80 Pa (high pressure) or 6.7 Pa (low pressure), were used. The chemical structure of the PECVD films was examined by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. The dielectric constant (ε r ) and dielectric loss (tan δ) of the films were investigated over a range of frequencies up to 1 MHz and the dielectric strength (breakdown voltage) (F b ) was characterized by the current-voltage method. Spectroscopic ellipsometry was performed to determine the film thickness and refractive index. Good dielectric properties were exhibited, as PP-benzene films formed in the high pressure, DS region showed a F b of 610 V/μm, an ε r of 3.07, and a tan δ of 7.0 x 10 -3 at 1 kHz. The PECVD processing pressure has a significant effect on final film structure and the film's physical density has a strong impact on dielectric breakdown strength. Also noted was that the residual oxygen content in the PP-benzene films significantly affected the frequency dependences of the dielectric constant and loss

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.

Axion-photon conversion in space and in low symmetrical dielectric crystals

International Nuclear Information System (INIS)

Gorelik, V S

2016-01-01

The opportunities of axions detection as the result of axion-photon conversion processes in the space and in low symmetrical dielectric crystals are discussed. In accordance with the modern theory predictions, axions are pseudoscalar vacuum particles having very small (0.001-1.0 meV) rest energy. The possibility of axions conversion into photons and vice-versa processes in vacuum at the presence of outer magnetic field has been analyzed before. Pseudoscalar (axion type) modes are existing in some types of crystals. Polar pseudoscalar lattice and exciton modes in low symmetrical crystals are strongly interacted with axions. In this work, optical excitation of axion-type modes in low symmetrical crystals is proposed for observation of axion - photon conversion processes. Instead of outer magnetic field, the crystalline field of such crystals may be used. The experimental schemes for axion-photon conversion processes observation with recording the secondary emission of luminescence, infrared or Stimulated Raman Scattering in some dielectric crystals are discussed. (paper)

Lipogels responsive to near-infrared light for the triggered release of therapeutic agents

NARCIS (Netherlands)

Martín-Saavedra, Francisco; Ruiz-Hernández, Eduardo; Escudero-Duch, Clara; Prieto, Martín; Arruebo, Manuel; Sadeghi, Negar; Deckers, Roel; Storm, Gert; Hennink, Wim E.; Santamaría, Jesús; Vilaboa, Nuria

2017-01-01

Here we report a composite system based on fibrin hydrogels that incorporate in their structure near-infrared (NIR) responsive nanomaterials and thermosensitive liposomes (TSL). Polymerized fibrin networks entrap simultaneously gold-based nanoparticles (NPs) capable of transducing NIR photon energy

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...

Electrowetting Variable Optics for Visible and Infrared Applications

Science.gov (United States)

Watson, Alexander Maxwell

Miniaturized variable optical devices are important for the fields of medical technology, optical communication, and consumer imaging devices. Areas ranging from endoscopy and optogenetics to atomic clocks and imaging all benefit from versatile optical systems. These applications all require precise and rapid control of imaging focal depth and lateral scanning. Electrowetting variable optics is one emergent technology that has the capability to provide focus tuning, beam steering, and even phase modulation in a small and robust package which requires no moving parts. Furthermore, electrowetting based devices there are attractive due to their transmissive nature, polarization insensitivity, low insertion loss, low electrical power requirements, and high optical quality. These features mean that electrowetting adaptive optical components are an attractive solution, compared with MEMS and liquid crystal optical components. Electrowetting is a technique that enables control of the shape of a liquid droplet with applied voltage. A conductive droplet on a dielectric surface alters its contact angle due to charges that build up between an underlying electrode and the surface of the droplet. This effect can be used to tune the curvature and tilt of liquids within cavities. The liquid boundary creates a high quality surface to use for lensing or steering applications. This thesis will focus on the development of electrowetting based lenses and prisms and applications in imaging for both visible and infrared wavelengths. Within this dissertation is the first demonstration of electrowetting lenses for phase control, as well as the investigation of non-aqueous electrowetting lens liquids for electrowetting lenses operation in the infrared. Key considerations that affect the performance and reliability are dielectric material and thickness, liquid selection and source of ionic conduction. The optical devices presented herein utilize judicious selection of dielectric material

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.

Influence of sodium dodecyl sulfate concentration on the photocatalytic activity and dielectric properties of intercalated sodium dodecyl sulfate into Zn–Cd–Al layered double hydroxide

Energy Technology Data Exchange (ETDEWEB)

Ahmed, Abdullah Ahmed Ali, E-mail: abdullah2803@gmail.com [Department of Physics, Faculty of Applied Science, Thamar University, Dhamar 87246 (Yemen); Talib, Zainal Abidin [Department of Physics, Faculty of Science, Universiti Putra Malaysia, UPM, Serdang, Selangor 43400 (Malaysia); Hussein, Mohd Zobir [Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, UPM, Serdang, Selangor 43400 (Malaysia)

2015-02-15

Highlights: • Zn–Cd–Al–LDH–DS were synthesized with different SDS concentrations. • Photocatalytic activity of samples was improved by increasing SDS concentration. • Dielectric response of LDH can be described by anomalous low frequency dispersion. • The dc conductivity values were calculated for Zn–Cd–Al–LDH–DS samples. • ESR spectra exhibited the successful intercalation of DS molecule into LDH gallery. - Abstract: Sodium dodecyl sulfate (SDS) has been successfully intercalated into Zn–Cd–Al–LDH precursor with different SDS concentrations (0.2, 0.3, 0.4, 0.5 and 1 mol L{sup −1}) using the coprecipitation method at (Zn{sup 2+} + Cd{sup 2+})/Al{sup 3+} molar ratio of 13 and pH 8. The structural, morphological, texture and composition properties of the synthesized (Zn–Cd–Al–LDH–DS) nanostructure were investigated using powder X-ray diffraction (PXRD), scanning electron microscope (SEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR), respectively. The photocatalytic activity of these materials was developed by increasing the concentration of intercalated SDS. The absorbance spectra have been used to detect an anion in the LDH interlayer before and after the intercalation process, which confirmed the presence of the dodecyl sulfate (DS{sup −}) anion into LDH gallery after intercalation. The anomalous low frequency dispersion (ALFD) has been used to describe the dielectric response of Zn–Cd–Al–LDH–DS nanostructure using the second type of universal power law. At low frequency, the polarization effect of electrodes caused the rising in dielectric constant and loss values. An important result of the dielectric measurements is the calculated dc conductivity values, which are new in dielectric spectroscopy of LDH materials. An important result of the electron spin resonance (ESR) spectra exhibited the successful intercalation of DS molecule into LDH gallery. The g-factor value was affected by

Infrared dielectric function of polydimethylsiloxane and selective emission behavior

Energy Technology Data Exchange (ETDEWEB)

Srinivasan, Arvind; Czapla, Braden; Narayanaswamy, Arvind, E-mail: arvind.narayanaswamy@columbia.edu [Department of Mechanical Engineering, Columbia University, New York, New York 10027 (United States); Mayo, Jeff [Skycatch, San Francisco, California 94107 (United States)

2016-08-08

The complex refractive index of polydimethylsiloxane (PDMS) is determined in the wavelength range between 2.5 μm and 16.7 μm. The parameters of a Drude-Lorentz oscillator model (with 15 oscillators) are extracted from Fourier transform infrared spectroscopy reflectance measurements made on both bulk PDMS and thin films of PDMS deposited on the gold coated silicon substrates. It is shown that thin films of PDMS atop gold exhibit selective emission in the 8 μm to 13 μm atmospheric transmittance window, which demonstrates that PDMS, especially due to its ease of deposition, may be a viable material for passive radiative cooling applications.

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.

Broadband infrared metamaterial absorber based on anodic aluminum oxide template

Science.gov (United States)

Yang, Jingfan; Qu, Shaobo; Ma, Hua; Wang, Jiafu; Yang, Shen; Pang, Yongqiang

2018-05-01

In this work, a broadband infrared metamaterial absorber is proposed based on trapezoid-shaped anodic aluminum oxide (AAO) template. Unlike traditional metamaterial absorber constructed from metal-dielectric-metal sandwich structure, our proposed absorber is composed of trapezoid-shaped AAO template with metallic nanowires inside. The infrared absorption efficiency is numerically calculated and the mechanism analysis is given in the paper. Owing to the superposition of multiple resonances produced by the nanowires with different heights, the infrared metamatrial absorber can keep high absorption efficiency during broad working wavelength band from 3.4 μm to 6.1 μm. In addition, the resonance wavelength is associated with the height of nanowires, which indicates that the resonance wavelength can be modulated flexibly through changing the heights of nanowires. This kind of design can also be adapted to other wavelength regions.

Far-Infrared Absorption of PbSe Nanorods

KAUST Repository

Hyun, Byung-Ryool

2011-07-13

Measurements of the far-infrared absorption spectra of PbSe nanocrystals and nanorods are presented. As the aspect ratio of the nanorods increases, the Fröhlich sphere resonance splits into two peaks. We analyze this splitting with a classical electrostatic model, which is based on the dielectric function of bulk PbSe but without any free-carrier contribution. Good agreement between the measured and calculated spectra indicates that resonances in the local field factors underlie the measured spectra. © 2011 American Chemical Society.

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.

Dielectric properties of (CuO,CaO2, and BaO)y/CuTl-1223 composites

International Nuclear Information System (INIS)

Mumtaz, M.; Kamran, M.; Nadeem, K.; Jabbar, Abdul; Khan, Nawazish A.; Saleem, Abida; Hussain, S.Tajammul; Kamran, M.

2013-01-01

We synthesized (CuO, CaO 2 , and BaO) y /Cu 0.5 Tl 0.5 Ba 2 Ca 2 Cu 3 O 10-δ (y = 0, 5%, 10%, 15%) composites by solid-state reaction and characterized by x-ray diffraction, scanning electron microscopy, dc-resistivity, and Fourier transform infrared spectroscopy. Frequency and temperature dependent dielectric properties such as real and imaginary part of dielectric constant, dielectric loss, and ac-conductivity of these composites are studied by capacitance and conductance measurement as a function of frequency (10 kHz to 10 MHz) and temperature (78 to 300 K). The x-ray diffraction analysis reveals that the characteristic behavior of Cu 0.5 Tl 0.5 Ba 2 Ca 2 Cu 3 O 10-δ superconductor phase and its structure is nearly undisturbed by doping of nanoparticles. The scanning electron microscopy images show the improvement in the intergranular links among the superconducting grains with increasing nanoparticles concentration. Microcracks are healed up with the inclusion of these nanoparticles and superconducting volume fraction is also increased. The dielectric properties of these composites strongly depend upon the frequency and temperature. The zero resistivity critical temperature and dielectric properties show opposite trend with the addition of nanoparticles in Cu 0.5 Tl 0.5 Ba 2 Ca 2 Cu 3 O 10-δ superconductor matrix.

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.

Far-infrared spectroscopy in ordered and disordered BaMg1/3Nb2/3O3 microwave ceramics

Science.gov (United States)

Dias, Anderson; Moreira, Roberto Luiz

2003-09-01

Ba(Mg1/3Nb2/3)O3 ceramics with suitable microwave dielectric properties for application in wireless communications and information access technologies were studied by far-infrared spectroscopy. Samples with different B-site ordering degrees, obtained by hydrothermal synthesis followed by sintering at various temperatures, were employed in this investigation. The sixteen infrared modes predicted by factor-group analysis were observed and adjusted according to a four-parameter semiquantum model. The dispersion parameters were determined in order to calculate the real part of the dielectric permittivity and the quality factors associated with the dielectric losses in the microwave region. The materials exhibited increasing ɛ0 and Q values up to 1100 °C, increasing more substantially when the temperature attained 1300 °C. The B-site ordering played an important role on this behavior along with the microstructural evolution above 1100 °C (grain growth), which also increased the phonon lifetime and contributed to the Q improvement. Kramers-Kronig analyses were carried out in all experimental data and the contributions of the main optical polar modes to the dielectric and microwave properties were carefully analyzed in order to identify and attribute the Ba-BO3 external mode, the inner modes related to the O-Mg-O and O-Nb-O bending vibrations, and the stretching modes of each MgO6 and NbO6 octahedron.

Lithium-doped hydroxyapatite nano-composites: Synthesis, characterization, gamma attenuation coefficient and dielectric properties

Science.gov (United States)

Badran, H.; Yahia, I. S.; Hamdy, Mohamed S.; Awwad, N. S.

2017-01-01

Lithium-hydroxyapatite (0, 1, 5, 10, 20, 30 and 40 wt% Li-HAp) nano-composites were synthesized by sol-gel technique followed by microwave-hydrothermal treatment. The composites were characterized by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) and Raman techniques. Gamma attenuation coefficient and the dielectric properties for all composites were investigated. The crystallinity degree of Li-doped HAp was higher than that of un-doped HAp. Gamma attenuation coefficient values increased from 0.562 cm-1 for 0 wt% Li-HAp to 2.190 cm-1 for 40 wt% Li-HAp. The alternating current conductivity increased with increasing frequency. The concentration of Li affect the values of dielectric constant where Li doped HAp of low dielectric constant can have an advantage for healing in bone fractures. The calcium to phosphorus ratio decreased from 1.43 to 1.37 with the addition of lithium indicating the Ca deficiency in the studied composites. Our findings lead to the conclusion that Li-HAp is a new nano-composite useful for medical applications and could be doped with gamma shield materials.

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

Nonlinear optics in germanium mid-infrared fiber material: Detuning oscillations in femtosecond mid-infrared spectroscopy

Directory of Open Access Journals (Sweden)

M. Ordu

2017-09-01

Full Text Available Germanium optical fibers hold great promise in extending semiconductor photonics into the fundamentally important mid-infrared region of the electromagnetic spectrum. The demonstration of nonlinear response in fabricated Ge fiber samples is a key step in the development of mid-infrared fiber materials. Here we report the observation of detuning oscillations in a germanium fiber in the mid-infrared region using femtosecond dispersed pump-probe spectroscopy. Detuning oscillations are observed in the frequency-resolved response when mid-infrared pump and probe pulses are overlapped in a fiber segment. The oscillations arise from the nonlinear frequency resolved nonlinear (χ(3 response in the germanium semiconductor. Our work represents the first observation of coherent oscillations in the emerging field of germanium mid-infrared fiber optics.

Facile synthesis, dielectric properties and electrocatalytic activities of PMMA-NiFe2O4 nanocomposite

International Nuclear Information System (INIS)

Maji, Pranabi; Choudhary, Ram Bilash

2017-01-01

The paper deals with the dielectric and catalytic properties of poly (methyl methacrylate)-nikel ferrite (PMMA-NiFe 2 O 4 ) nanocomposite. The nanocomposite was prepared by using a general and facile synthesis strategy. Fourier transform infrared (FTIR) and X-ray diffraction (XRD) spectra confirmed the formation of PMMA-NiFe 2 O 4 nanocomposite. Field effect scanning electron microscopic (FESEM) and transmission electron microscopic (TEM) images revealed that NiFe 2 O 4 nanoparticles were uniformly distributed and were tightly adhered with PMMA matrix owing to surface modification with 3-methacryloyloxy propyl trimethoxy silane (KH-570). Thermal stability was enhanced by incorporation of NiFe 2 O 4 nanofillers. The nanocomposite showed high dielectric constant and low dielectric loss. The achieved dielectric and thermal property inferred the potential application of this material in energy storage and embedded electronics devices. Further, the as prepared nanocomposite also offered a remarkable electrochemical performance towards hydrogen peroxide (H 2 O 2 ) sensing. - Highlights: • PMMA-NiFe 2 O 4 nanocomposite was synthesized via free radical polymerization. • The nanocomposite exhibited high value of dielectric constant (51) and tanδ (0.3). • Thermal stability of the PMMA matrix was improved by the incorporation of NiFe 2 O 4. • The H 2 O 2 detection limit was estimated 44 μM when signal to noise (S/N) ration was 3. • The electrochemical sensitivity of H 2 O 2 was calculated 0.6727 μA mM -1 .

Functional Design of Dielectric-Metal-Dielectric-Based Thin-Film Encapsulation with Heat Transfer and Flexibility for Flexible Displays.

Science.gov (United States)

Kwon, Jeong Hyun; Choi, Seungyeop; Jeon, Yongmin; Kim, Hyuncheol; Chang, Ki Soo; Choi, Kyung Cheol

2017-08-16

In this study, a new and efficient dielectric-metal-dielectric-based thin-film encapsulation (DMD-TFE) with an inserted Ag thin film is proposed to guarantee the reliability of flexible displays by improving the barrier properties, mechanical flexibility, and heat dissipation, which are considered to be essential requirements for organic light-emitting diode (OLED) encapsulation. The DMD-TFE, which is composed of Al 2 O 3 , Ag, and a silica nanoparticle-embedded sol-gel hybrid nanocomposite, shows a water vapor transmission rate of 8.70 × 10 -6 g/m 2 /day and good mechanical reliability at a bending radius of 30 mm, corresponding to 0.41% strain for 1000 bending cycles. The electrical performance of a thin-film encapsulated phosphorescent organic light-emitting diode (PHOLED) was identical to that of a glass-lid encapsulated PHOLED. The operational lifetimes of the thin-film encapsulated and glass-lid encapsulated PHOLEDs are 832 and 754 h, respectively. After 80 days, the thin-film encapsulated PHOLED did not show performance degradation or dark spots on the cell image in a shelf-lifetime test. Finally, the difference in lifetime of the OLED devices in relation to the presence and thickness of a Ag film was analyzed by applying various TFE structures to fluorescent organic light-emitting diodes (FOLEDs) that could generate high amounts of heat. To demonstrate the difference in heat dissipation effect among the TFE structures, the saturated temperatures of the encapsulated FOLEDs were measured from the back side surface of the glass substrate, and were found to be 67.78, 65.12, 60.44, and 39.67 °C after all encapsulated FOLEDs were operated at an initial luminance of 10 000 cd/m 2 for sufficient heat generation. Furthermore, the operational lifetime tests of the encapsulated FOLED devices showed results that were consistent with the measurements of real-time temperature profiles taken with an infrared camera. A multifunctional hybrid thin-film encapsulation

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.

Comparison of neat and photo-crosslinked polyvinylidene fluoride-co-hexafluoropropylene thin film dielectrics formed by spin-coating

International Nuclear Information System (INIS)

Iyore, O.D.; Roodenko, K.; Winkler, P.S.; Noriega, J.R.; Vasselli, J.J.; Chabal, Y.J.; Gnade, B.E.

2013-01-01

We report the characterization of photo-crosslinked polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) thin film, metal–insulator–metal capacitors fabricated using standard semiconductor processing techniques. We characterize the capacitors using in-situ vibrational spectroscopy during thermally-assisted poling and correlate the Fourier transform infrared spectroscopy (FTIR) results with X-ray diffraction (XRD) results. FTIR analysis of the neat PVDF-HFP showed α → β transformations during poling at room temperature and at 55 °C. α → β transformations were observed for the crosslinked polymer only during poling at 55 °C. XRD data revealed that photo-crosslinking caused the polymer to partially crystallize into the β-phase. The similar behavior of the neat and crosslinked samples at 55 °C suggests that a higher activation energy was needed for α → β transformations in crosslinked PVDF-HFP during poling. Electrical measurements showed that photo-crosslinking had no significant effect on the dielectric constant and dielectric loss of PVDF-HFP. However, the dielectric strength and maximum energy density of the crosslinked polymer were severely reduced. - Highlights: • Polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) dielectrics were studied. • Phase transformations were observed only at 55 °C for the crosslinked PVDF-HFP. • Crosslinking had no strong effect on the dielectric constant of PVDF-HFP. • Breakdown strengths were 620 MVm −1 and 362 MVm −1 for neat and crosslinked films

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

AC electrical conductivity and dielectric relaxation studies on n-type organic thin films of N, N‧-Dimethyl-3,4,9,10-perylenedicarboximide (DMPDC)

Science.gov (United States)

Qashou, Saleem I.; Darwish, A. A. A.; Rashad, M.; Khattari, Z.

2017-11-01

Both Alternating current (AC) conductivity and dielectric behavior of n-type organic thin films of N, N‧-Dimethyl-3,4,9,10-perylenedicarboximide (DMPDC) have been investigated. Fourier transformation infrared (FTIR) spectroscopy is used for identifying both powder and film bonds which confirm that there are no observed changes in the bonds between the DMPDC powder and evaporated films. The dependence of AC conductivity on the temperature for DMPDC evaporated films was explained by the correlated barrier hopping (CBH) model. The calculated barrier height using CBH model shows a decreasing behavior with increasing temperature. The mechanism of dielectric relaxation was interpreted on the basis of the modulus of the complex dielectric. The calculated activation energy of the relaxation process was found to be 0.055 eV.

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.

Polymer-Ceramic Composite Materials for Pyroelectric Infrared Detectors: An Overview

Science.gov (United States)

Aggarwal, M. D; Currie, J. R.; Penn, B. G.; Batra, A. K.; Lal, R. B.

2007-01-01

Ferroelectrics:Polymer composites can be considered an established substitute for conventional electroceramics and ferroelectric polymers. The composites have a unique blend of polymeric properties such as mechanical flexibility, high strength, formability, and low cost, with the high electro-active properties of ceramic materials. They have attracted considerable interest because of their potential use in pyroelectric infrared detecting devices and piezoelectric transducers. These flexible sensors and transducers may eventually be useful for their health monitoring applications for NASA crew launch vehicles and crew exploration vehicles being developed. In the light of many technologically important applications in this field, it is worthwhile to present an overview of the pyroelectric infrared detector theory, models to predict dielectric behavior and pyroelectric coefficient, and the concept of connectivity and fabrication techniques of biphasic composites. An elaborate review of Pyroelectric-Polymer composite materials investigated to date for their potential use in pyroelectric infrared detectors is presented.

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.

Waveguide resonances with selectable polarization in an infrared thermal emitter

Directory of Open Access Journals (Sweden)

Wei-Lun Huang

2017-08-01

Full Text Available A multi-band infrared thermal emitter with polarized waveguide resonances was investigated. The device is constructed by embedding the metallic grating strips within the resonant cavity of a metal/dielectric/metal (MDM structure. The proposed arrangement makes it possible to generate waveguide resonances with mutually orthogonal polarization, thereby providing an additional degree of freedom to vary the resonant wavelengths and polarizations in the medium infrared region. The measured reflection spectra and the finite-difference time-domain (FDTD simulation indicated that the electric fields of the waveguide modes with two orthogonal polarizations are distributed in different regions of the cavity. Resonant wavelengths in different polarizations can be adjusted by altering the period, the metallic line width, or the position of the embedded gold strips. The ratio of the full width at half maximum (FWHM to the peak wavelength was achieved to be smaller than 0.035. This study demonstrated a multi-band infrared thermal emission featuring a narrow bandwidth and polarization characteristics, which is quite suitable to be applied to the non-dispersive infrared (NDIR detection system.

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.

Charge distribution and response time for a modulation-doped extrinsic infrared detector

Science.gov (United States)

Hadek, Victor

1987-01-01

The electric charge distribution and response time of a modulation-doped extrinsic infrared detector are determined. First, it is demonstrated theoretically that the photoconductive layer is effectively depleted of ionized majority-impurity charges so that scattering is small and mobility is high for photogenerated carriers. Then, using parameters appropriate to an actual detector, the predicted response time is 10 to the -8th to about 10 to the -9th s, which is much faster than comparable conventional detectors. Thus, the modulation-doped detector design would be valuable for heterodyne applications.

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.

3D-Printing of inverted pyramid suspending architecture for pyroelectric infrared detectors with inhibited microphonic effect

Science.gov (United States)

Xu, Qing; Zhao, Xiangyong; Li, Xiaobing; Deng, Hao; Yan, Hong; Yang, Linrong; Di, Wenning; Luo, Haosu; Neumann, Norbert

2016-05-01

A sensitive chip with ultralow dielectric loss based on Mn doped PMNT (71/29) has been proposed for high-end pyroelectric devices. The dielectric loss at 1 kHz is 0.005%, one order lower than the minimum value reported so far. The detective figure of merit (Fd) is up to 92.6 × 10-5 Pa-1/2 at 1 kHz and 53.5 × 10-5 Pa-1/2 at 10 Hz, respectively. In addition, an inverted pyramid suspending architecture for supporting the sensitive chip has been designed and manufactured by 3D printing technology. The combination of this sensitive chip and the proposed suspending architecture largely enhances the performance of the pyroelectric detectors. The responsivity and specific detectivity are 669,811 V/W and 3.32 × 109 cm Hz1/2/W at 10 Hz, respectively, 1.9 times and 1.5 times higher than those of the highest values in literature. Furthermore, the microphonic effect can be largely inhibited according to the theoretical and experimental analysis. This architecture will have promising applications in high-end and stable pyroelectric infrared detectors.

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.

Spectral response, dark current, and noise analyses in resonant tunneling quantum dot infrared photodetectors.

Science.gov (United States)

Jahromi, Hamed Dehdashti; Mahmoodi, Ali; Sheikhi, Mohammad Hossein; Zarifkar, Abbas

2016-10-20

Reduction of dark current at high-temperature operation is a great challenge in conventional quantum dot infrared photodetectors, as the rate of thermal excitations resulting in the dark current increases exponentially with temperature. A resonant tunneling barrier is the best candidate for suppression of dark current, enhancement in signal-to-noise ratio, and selective extraction of different wavelength response. In this paper, we use a physical model developed by the authors recently to design a proper resonant tunneling barrier for quantum infrared photodetectors and to study and analyze the spectral response of these devices. The calculated transmission coefficient of electrons by this model and its dependency on bias voltage are in agreement with experimental results. Furthermore, based on the calculated transmission coefficient, the dark current of a quantum dot infrared photodetector with a resonant tunneling barrier is calculated and compared with the experimental data. The validity of our model is proven through this comparison. Theoretical dark current by our model shows better agreement with the experimental data and is more accurate than the previously developed model. Moreover, noise in the device is calculated. Finally, the effect of different parameters, such as temperature, size of quantum dots, and bias voltage, on the performance of the device is simulated and studied.

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

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

Far-infrared reflection-absorption spectroscopy of amorphous and polycrystalline gallium arsenide films

International Nuclear Information System (INIS)

Gregory, J.R.

1992-01-01

We have reported far-infrared reflection absorption spectra (30-320CM -1 ) at 30 and 310K for nine films of non-stoichiometric GaAs. The FIRRAS measurements were performed using the grazing incidence FIR double-modulation spectroscopy technique first described by DaCosta and Coleman. The films were fabricated by molecular beam deposition on metallized substrates for two As/Ga molecular beam flux ratios. The films were characterized by depth profilometry, IRAS, XRD, and x-ray microprobe analysis. Film thicknesses ranged from 800 to 5800 angstrom and compositions were 45-50% As for a MB flux ratio of 0.29 and 60-70% As for a ratio of 1.12. FIRRAS measurements were made and characterizations performed for as-deposited films and for 5 hour anneals at 473, 573, 673 and 723 degrees C. Vibrational spectra of the crystallized films were interpreted in terms of the exact reflectivity of a thin dielectric film on a conducting substrate, using a classical Lorentzian dielectric function for the response of the film. Resonances appearing in the open-quote forbidden close-quote region between the TO and LO frequencies were modelled with an effective medium approximation and are interpreted as arising from small-scale surface roughness. The behavior of the amorphous film spectra were examined within two models. The effective force constant model describes the variation of the reflection-absorption maxima with measured crystallite size in terms of the effective vibration frequency of 1-D atomic chains having force constants distributed according to the parameters of the crystalline-to-amorphous relaxation length and the crystalline to amorphous force constant ratio. The dielectric function continuum model uses the relaxation of the crystal momentum selection rule to calculate the reflection-absorption spectrum based on a dielectric function in which the oscillator strength is the normalized product of a constant dipole strength and the smoothed vibrational density of states

Low-loss, infrared and terahertz nanophotonics using surface phonon polaritons

Directory of Open Access Journals (Sweden)

Caldwell Joshua D.

2015-04-01

Full Text Available The excitation of surface-phonon-polariton (SPhP modes in polar dielectric crystals and the associated new developments in the field of SPhPs are reviewed. The emphasis of this work is on providing an understanding of the general phenomenon, including the origin of the Reststrahlen band, the role that optical phonons in polar dielectric lattices play in supporting sub-diffraction-limited modes and how the relatively long optical phonon lifetimes can lead to the low optical losses observed within these materials. Based on this overview, the achievements attained to date and the potential technological advantages of these materials are discussed for localized modes in nanostructures, propagating modes on surfaces and in waveguides and novel metamaterial designs, with the goal of realizing low-loss nanophotonics and metamaterials in the mid-infrared to terahertz spectral ranges.

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

Preparation and Preliminary Dielectric Characterization of Structured C60-Thiol-Ene Polymer Nanocomposites Assembled Using the Thiol-Ene Click Reaction

Directory of Open Access Journals (Sweden)

Hanaa M. Ahmed

2015-11-01

Full Text Available Fullerene-containing materials have the ability to store and release electrical energy. Therefore, fullerenes may ultimately find use in high-voltage equipment devices or as super capacitors for high electric energy storage due to this ease of manipulating their excellent dielectric properties and their high volume resistivity. A series of structured fullerene (C60 polymer nanocomposites were assembled using the thiol-ene click reaction, between alkyl thiols and allyl functionalized C60 derivatives. The resulting high-density C60-urethane-thiol-ene (C60-Thiol-Ene networks possessed excellent mechanical properties. These novel networks were characterized using standard techniques, including infrared spectroscopy (FTIR, differential scanning calorimetry (DSC, dynamic mechanical analysis (DMA, and thermal gravimetric analysis (TGA. The dielectric spectra for the prepared samples were determined over a broad frequency range at room temperature using a broadband dielectric spectrometer and a semiconductor characterization system. The changes in thermo-mechanical and electrical properties of these novel fullerene-thiol-ene composite films were measured as a function of the C60 content, and samples characterized by high dielectric permittivity and low dielectric loss were produced. In this process, variations in chemical composition of the networks were correlated to performance characteristics.

Surface plasmon polariton amplification in semiconductor-graphene-dielectric structure

Energy Technology Data Exchange (ETDEWEB)

Dadoenkova, Yuliya S. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Novgorod State University, Veliky Novgorod (Russian Federation); Donetsk Institute for Physics and Technology, Donetsk (Ukraine); Moiseev, Sergey G. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Kotelnikov Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Ulyanovsk (Russian Federation); Abramov, Aleksei S. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Kadochkin, Aleksei S.; Zolotovskii, Igor O. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Institute of Nanotechnologies of Microelectronics of the Russian Academy of Sciences, 32A Leninskiy Prosp., 119991, Moscow (Russian Federation); Fotiadi, Andrei A. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Universite de Mons (Belgium)

2017-05-15

A mechanism of amplification of surface plasmon polaritons due to the transfer of electromagnetic energy from a drift current wave into a far-infrared surface wave propagating along a semiconductor-dielectric boundary in waveguide geometry is proposed. A necessary condition of the interaction of these waves is phase matching condition, i. e., when the phase velocity of the surface wave approaches the drift velocity of charge carriers. It is shown that in the spectral region of the surface plasmon polariton slowing-down its amplification coefficient can reach values substantially exceeding the ohmic loss coefficient of the surface wave in the structure. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

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....

Broad-band dielectric response of 0.5Ba(Ti.sub.0.8./sub.Zr.sub.0.2./sub.)O-.sub.3./sub.-0.5(Ba.sub.0.7./sub.Ca.sub.0.3./sub.)TiO.sub.3./sub. piezoceramics: soft and central mode behaviour

Czech Academy of Sciences Publication Activity Database

Kamba, Stanislav; Simon, Elizabeth; Skoromets, Volodymyr; Bovtun, Viktor; Kempa, Martin; Pokorný, Jan; Savinov, Maxim; Koruza, J.; Malič, B.

2016-01-01

Roč. 89, č. 7-8 (2016), s. 785-793 ISSN 0141-1594 R&D Projects: GA MŠk(CZ) LD15014 Institutional support: RVO:68378271 Keywords : Dielectric spectroscopy * lead- free piezoelectrics * soft mode * central mode * phonons * polar nanoregions * infrared * terahertz * Raman spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.060, year: 2016

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...

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).

Comparison of neat and photo-crosslinked polyvinylidene fluoride-co-hexafluoropropylene thin film dielectrics formed by spin-coating

Energy Technology Data Exchange (ETDEWEB)

Iyore, O.D.; Roodenko, K.; Winkler, P.S. [Materials Science and Engineering Department, The University of Texas at Dallas, Richardson, TX 75080 (United States); Noriega, J.R.; Vasselli, J.J. [Electrical Engineering Department, The University of Texas at Tyler, Tyler, TX 75799 (United States); Chabal, Y.J. [Materials Science and Engineering Department, The University of Texas at Dallas, Richardson, TX 75080 (United States); Gnade, B.E., E-mail: gnade@utdallas.edu [Materials Science and Engineering Department, The University of Texas at Dallas, Richardson, TX 75080 (United States)

2013-12-02

We report the characterization of photo-crosslinked polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) thin film, metal–insulator–metal capacitors fabricated using standard semiconductor processing techniques. We characterize the capacitors using in-situ vibrational spectroscopy during thermally-assisted poling and correlate the Fourier transform infrared spectroscopy (FTIR) results with X-ray diffraction (XRD) results. FTIR analysis of the neat PVDF-HFP showed α → β transformations during poling at room temperature and at 55 °C. α → β transformations were observed for the crosslinked polymer only during poling at 55 °C. XRD data revealed that photo-crosslinking caused the polymer to partially crystallize into the β-phase. The similar behavior of the neat and crosslinked samples at 55 °C suggests that a higher activation energy was needed for α → β transformations in crosslinked PVDF-HFP during poling. Electrical measurements showed that photo-crosslinking had no significant effect on the dielectric constant and dielectric loss of PVDF-HFP. However, the dielectric strength and maximum energy density of the crosslinked polymer were severely reduced. - Highlights: • Polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) dielectrics were studied. • Phase transformations were observed only at 55 °C for the crosslinked PVDF-HFP. • Crosslinking had no strong effect on the dielectric constant of PVDF-HFP. • Breakdown strengths were 620 MVm{sup −1} and 362 MVm{sup −1} for neat and crosslinked films.

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.

Modification of the refractive index and the dielectric constant of silicon dioxide by means of ion implantation

International Nuclear Information System (INIS)

Swart, J.W.; Diniz, J.A.; Doi, I.; Moraes, M.A.B. de

2000-01-01

The modification of silicon dioxide films by means of ion implantation of fluorine and carbon was studied. 19 F + and 12 C + ions were separately and sequentially implanted in 250 nm thick thermal SiO 2 films with energies ranging from 10 to 50 keV and fluences in the interval 5x10 15 to 5x10 16 cm -2 . Metal/oxide/semiconductor (MOS) capacitors were fabricated on half side of the wafers. The implanted SiO 2 /Si samples were characterized by means of ellipsometry and Fourier transform infrared (FTIR) spectroscopy. The MOS capacitors were used to determine the relative dielectric constant. Our results indicate a considerable reduction of the dielectric constant and refractive index. The refractive index was reduced from 1.46 to 1.29 when only fluorine was implanted or when fluorine with a higher dose was implanted in combination with carbon. For the same conditions, a relative dielectric constant of 3.4 was obtained and a shift in the Si-O bond stretching mode from 1085 to 1075 cm -1 was observed by FTIR spectroscopy

Mesoscopic modeling of the response of human dental enamel to mid-infrared radiation

Science.gov (United States)

Vila Verde, Ana; Ramos, Marta; Stoneham, A. M.

2006-03-01

Ablation of human dental enamel, a composite biomaterial with water pores, is of significant importance in minimally invasive laser dentistry but progress in the area is hampered by the lack of optimal laser parameters. We use mesoscopic finite element models of this material to study its response to mid-infrared radiation. Our results indicate that the cost-effective, off-the-shelf CO2 laser at λ = 10.6 μm may in fact ablate enamel precisely, reproducibly and with limited unwanted side effects such as cracking or heating, provided that a pulse duration of 10 μs is used. Furthermore, our results also indicate that the Er:YAG laser (λ = 2.94 μm), currently popular for laser dentistry, may in fact cause unwanted deep cracking in the enamel when regions with unusually high water content are irradiated, and also provide an explanation for the large range of ablation threshold values observed for this material. The model may be easily adapted to study the response of any composite material to infrared radiation and thus may be useful for the scientific community.

Mid-infrared response of reduced graphene oxide and its high-temperature coefficient of resistance

Directory of Open Access Journals (Sweden)

Haifeng Liang

2014-10-01

Full Text Available Much effort has been made to study the formation mechanisms of photocurrents in graphene and reduced graphene oxide films under visible and near-infrared light irradiation. A built-in field and photo-thermal electrons have been applied to explain the experiments. However, much less attention has been paid to clarifying the mid-infrared response of reduced graphene oxide films at room temperature. Thus, mid-infrared photoresponse and annealing temperature-dependent resistance experiments were carried out on reduced graphene oxide films. A maximum photocurrent of 75 μA was observed at room temperature, which was dominated by the bolometer effect, where the resistance of the films decreased as the temperature increased after they had absorbed light. The electrons localized in the defect states and the residual oxygen groups were thermally excited into the conduction band, forming a photocurrent. In addition, a temperature increase of 2 °C for the films after light irradiation for 2 minutes was observed using absorption power calculations. This work details a way to use reduced graphene oxide films that contain appropriate defects and residual oxygen groups as bolometer-sensitive materials in the mid-infrared range.

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)

Near-infrared light-responsive dynamic wrinkle patterns.

Science.gov (United States)

Li, Fudong; Hou, Honghao; Yin, Jie; Jiang, Xuesong

2018-04-01

Dynamic micro/nanopatterns provide an effective approach for on-demand tuning of surface properties to realize a smart surface. We report a simple yet versatile strategy for the fabrication of near-infrared (NIR) light-responsive dynamic wrinkles by using a carbon nanotube (CNT)-containing poly(dimethylsiloxane) (PDMS) elastomer as the substrate for the bilayer systems, with various functional polymers serving as the top stiff layers. The high photon-to-thermal energy conversion of CNT leads to the NIR-controlled thermal expansion of the elastic CNT-PDMS substrate, resulting in dynamic regulation of the applied strain (ε) of the bilayer system by the NIR on/off cycle to obtain a reversible wrinkle pattern. The switchable surface topological structures can transfer between the wrinkled state and the wrinkle-free state within tens of seconds via NIR irradiation. As a proof-of-concept application, this type of NIR-driven dynamic wrinkle pattern was used in smart displays, dynamic gratings, and light control electronics.

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)

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.

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.

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.

Direct Fabrication of Inkjet-Printed Dielectric Film for Metal-Insulator-Metal Capacitors

Science.gov (United States)

Cho, Cheng-Lin; Kao, Hsuan-ling; Wu, Yung-Hsien; Chang, Li-Chun; Cheng, Chun-Hu

2018-01-01

In this study, an inkjet-printed dielectric film that used a polymer-based SU-8 ink was fabricated for use in a metal-insulator-metal (MIM) capacitor. Thermal treatment of the inkjet-printed SU-8 polymer film affected its surface morphology, chemical structure, and surface wettability. A 20-min soft-bake at 60°C was applied to eliminate inkjet-printed bubbles and ripples. The ultraviolet-exposed SU-8 polymer film was crosslinked at temperatures between 120°C and 220°C and became disordered at 270°C, demonstrated using Fourier-transform infrared spectroscopy. A maximum SU-8 polymer film hard-bake temperature of 120°C was identified, and a printing process was subsequently employed because the appropriate water contact angle of the printed film was 79°. Under the appropriate inkjet printing conditions, the two-transmission-line method was used to extract the dielectric and electrical properties of the SU-8 polymer film, and the electrical behavior of the fabricated MIM capacitor was also characterized.

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.)

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.

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.

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)

Dielectric laser acceleration of non-relativistic electrons at a photonic structure

Energy Technology Data Exchange (ETDEWEB)

Breuer, John

2013-08-29

This thesis reports on the observation of dielectric laser acceleration of non-relativistic electrons via the inverse Smith-Purcell effect in the optical regime. Evanescent modes in the vicinity of a periodic grating structure can travel at the same velocity as the electrons along the grating surface. A longitudinal electric field component is used to continuously impart momentum onto the electrons. This is only possible in the near-field of a suitable photonic structure, which means that the electron beam has to pass the structure within about one wavelength. In our experiment we exploit the third spatial harmonic of a single fused silica grating excited by laser pulses derived from a Titanium:sapphire oscillator and accelerate non-relativistic 28 keV electrons. We measure a maximum energy gain of 280 eV, corresponding to an acceleration gradient of 25 MeV/m, already comparable with state-of-the-art radio-frequency linear accelerators. To experience this acceleration gradient the electrons approach the grating closer than 100 nm. We present the theory behind grating-based particle acceleration and discuss simulation results of dielectric laser acceleration in the near-field of photonic grating structures, which is excited by near-infrared laser light. Our measurements show excellent agreement with our simulation results and therefore confirm the direct acceleration with the light field. We further discuss the acceleration inside double grating structures, dephasing effects of non-relativistic electrons as well as the space charge effect, which can limit the attainable peak currents of these novel accelerator structures. The photonic structures described in this work can be readily concatenated and therefore represent a scalable realization of dielectric laser acceleration. Furthermore, our structures are directly compatible with the microstructures used for the acceleration of relativistic electrons demonstrated in parallel to this work by our collaborators in

Photoperiodic responses of Kalanchoe and chrysanthemum to radiation by an infrared lamp

International Nuclear Information System (INIS)

Ko, C.H.; Lee, S.B.; Jeong, B.R.

2012-01-01

This experiment was conducted to investigate the effect of a low intensity infrared radiation on the growth and photoperiodic responses of Kalanchoe blossfeldiana ‘Kaluna’ and ‘Taos’, and Dendranthema grandiflorum ‘Lemon Eye’ grown in growth chambers. In the first experiment, uniformly-rooted cuttings of ‘Kaluna’ and ‘Lemon Eye’ were selected and transplanted to 10 cm pots. After a week, pots were transferred from greenhouse to three environment-controlled growth chambers. All chambers were maintained at 25 ± 1 and 70% RH with an 8 hours photoperiod (760 μmol·m −2 ·s −1 ), provided by high pressure sodium and white fluorescent lamps. During the night period one chamber was left unlit (darkness), while the second and third ones were lit with an incandescent lamp (10 μmol·m −2 ·s −1 ) or an infrared lamp (15 μmol·m −2 ·s −1 ), respectively. Shoot length, root length, stem diameter, number of flowers, number of branches, fresh weight, and dry weight were measured after eight weeks. Flowering occurred on plants maintained in the unlit darkness and under an incandescent lamp during the night period, while only vegetative growth was observed under an infrared lamp. In the second experiment, cuttings of uniformly-rooted ‘Taos’ and ‘Lemon Eye’ were selected and transferred from the greenhouse to three environment-controlled growth chambers with the same environment setting as in the first experiment at a week after potting. During the night period one chamber was left unlit (darkness), the second and third ones were lit with an incandescent or an infrared heating lamp, both at a 0.3 μmol·m −2 ·s −1 PPFD level. After nine weeks, flowering in all treatments was observed, but was slightly delayed under an incandescent and an infrared heating lamp. Because both the incandescent lamp and the infrared lamp slightly delayed flowering in these two species, a more detailed experiment is necessary to find out at which

Infrared reflectance measurement for InN thin film characterization

International Nuclear Information System (INIS)

Fukui, K.; Kugumiya, Y.; Nakagawa, N.; Yamamoto, A.

2006-01-01

Infrared reflectance measurements of a series of InN thin films have been performed and attempt to derive carrier concentration and other physical constants for InN thin film characterization. Fitting calculations are performed by use of the dielectric function equation based on phonon-plasmon coupling model. Longitudinal and transverse optical phonon frequencies, plasma frequency and their damping parameters can be derived from fitting. From those results, electrical and phonon properties of InN and characterization of films are discussed. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

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...

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)

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.

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.

Linear and non-linear infrared response of one-dimensional vibrational Holstein polarons in the anti-adiabatic limit: Optical and acoustical phonon models

Science.gov (United States)

Falvo, Cyril

2018-02-01

The theory of linear and non-linear infrared response of vibrational Holstein polarons in one-dimensional lattices is presented in order to identify the spectral signatures of self-trapping phenomena. Using a canonical transformation, the optical response is computed from the small polaron point of view which is valid in the anti-adiabatic limit. Two types of phonon baths are considered: optical phonons and acoustical phonons, and simple expressions are derived for the infrared response. It is shown that for the case of optical phonons, the linear response can directly probe the polaron density of states. The model is used to interpret the experimental spectrum of crystalline acetanilide in the C=O range. For the case of acoustical phonons, it is shown that two bound states can be observed in the two-dimensional infrared spectrum at low temperature. At high temperature, analysis of the time-dependence of the two-dimensional infrared spectrum indicates that bath mediated correlations slow down spectral diffusion. The model is used to interpret the experimental linear-spectroscopy of model α-helix and β-sheet polypeptides. This work shows that the Davydov Hamiltonian cannot explain the observations in the NH stretching range.

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

Far-infrared spectroscopic study of CeO2 nanocrystals

International Nuclear Information System (INIS)

Popović, Z. V.; Grujić-Brojčin, M.; Paunović, N.; Radonjić, M. M.; Araújo, V. D.; Bernardi, M. I. B.; Lima, M. M. de; Cantarero, A.

2015-01-01

We present the far-infrared reflectivity spectra of 5 nm-sized pure and copper-doped Ce 1−x Cu x O 2−y (x = 0; 0.01 and 0.10) nanocrystals measured at room temperature in the 50–650 cm −1 spectral range. Reflectivity spectra were analyzed using the factorized form of the dielectric function, which includes the phonon and the free carriers contribution. Four oscillators with TO energies of approximately 135, 280, 370, and 490 cm −1 were included in the fitting procedure. These oscillators represent local maxima of the CeO 2 phonon density of states, which is also calculated using the density functional theory. The lowest energy oscillator represents TA(L)/TA(X) phonon states, which become infrared-active E u modes at the L and X points of the Brillouin zone (BZ). The second oscillator originates from TO(Γ) phonon states. The oscillator at ∼400 cm −1 originates from Raman mode phonon states, which at the L point of BZ also becomes infrared-active E u mode. The last oscillator describes phonons with dominantly LO(Γ) infrared mode character. The appearance of phonon density of states related oscillators, instead of single F 2u infrared-active mode in the far-infrared reflectivity spectra, is a consequence of the nanosized dimension of the CeO 2 particles. The best fit spectra are obtained using the generalized Bruggeman model for inhomogeneous media, which takes into account the nanocrystal volume fraction and the pore shape

Infrared spectroscopy and density functional theory investigation of calcite, chalk, and coccoliths-do we observe the mineral surface?

DEFF Research Database (Denmark)

Andersson, Martin Peter; Hem, Caroline Piper; Schultz, Logan Nicholas

2014-01-01

broadening from macroscopic dielectric effects. We detect water adsorbed on the high surface area synthetic calcite, which permits observation of the chemistry of thin liquid films on calcite using transmission infrared spectroscopy. The combination of infrared spectroscopy and density functional theory also...... asymmetric for the coccoliths and the synthetic calcite prepared using the carbonation method. It can be very well fitted by two peaks: a narrow Lorenzian at lower frequency and a broader Gaussian at higher frequency. These two samples both have a high specific surface area. Density functional theory...

Near-Infrared and Optical Beam Steering and Frequency Splitting in Air-Holes-in-Silicon Inverse Photonic Crystals

Science.gov (United States)

2017-01-01

We present the design of a dielectric inverse photonic crystal structure that couples line-defect waveguide propagating modes into highly directional beams of controllable directionality. The structure utilizes a triangular lattice made of air holes drilled in an infinitely thick Si slab, and it is designed for operation in the near-infrared and optical regime. The structure operation is based on the excitation and manipulation of dark dielectric surface states, in particular on the tailoring of the dark states’ coupling to outgoing radiation. This coupling is achieved with the use of properly designed external corrugations. The structure adapts and matches modes that travel through the photonic crystal and the free space. Moreover it facilitates the steering of the outgoing waves, is found to generate well-defined, spatially and spectrally isolated beams, and may serve as a frequency splitting component designed for operation in the near-infrared regime and in particular the telecom optical wavelength band. The design complies with the state-of-the-art Si nanofabrication technology and can be directly scaled for operation in the optical regime. PMID:29541653

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.

High Dielectric Constant Study of TiO2-Polypyrrole Composites with Low Contents of Filler Prepared by In Situ Polymerization

Directory of Open Access Journals (Sweden)

Khalil Ahmed

2016-01-01

Full Text Available TiO2/polypyrrole composites with high dielectric constant have been synthesized by in situ polymerization of pyrrole in an aqueous dispersion of low concentration of TiO2, in the presence of small amount of HCl. Structural, optical, surface morphological, and thermal properties of the composites were investigated by X-ray diffractometer, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, and thermogravimetric analysis, respectively. The data obtained from diffractometer and thermal gravimetric analysis confirmed the crystalline nature and thermal stability of the prepared composites. The dielectric constant of 5 wt% TiO2 increased with filler content up to 4.3 × 103 at 1 kHz and then decreased to 1.25 × 103 at 10 kHz.

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).

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.

Laser radiation effect on radiation-induced defects in heavy ion tracks in dielectrics

International Nuclear Information System (INIS)

Egorov, A.N.; Zhiryakov, B.M.; Kushin, V.V.; Lyapidevskij, V.K.; Khokhlov, N.B.

1988-01-01

Possibility of laser radiation resonance effect on radiation-induced defects in heavy ion tracks in dielectric materials is investigated. Absorption spectra in infrared, visible and ultraviolet ranges for cellulose nitrate samples irradiated by 6 MeV/nucleon 58 Ni ions and reactor gamma radiation are measured. Absorption spectra for irradiated and reference samples are presented. Two absorption bands λ 1 =0.33 μm (E 1 =3.9 eV) and λ 2 =0.72 μm (E 2 =1.7 eV) are detected. Etching rate decrease in a track under laser radiation effect is noticed. 3 refs.; 1 fig

High-efficient light absorption of monolayer graphene via cylindrical dielectric arrays and the sensing application

Science.gov (United States)

Zhou, Peng; Zheng, Gaige

2018-04-01

The efficiency of graphene-based optoelectronic devices is typically limited by the poor absolute absorption of light. A hybrid structure of monolayer graphene with cylindrical titanium dioxide (TiO2) array and aluminum oxide (Al2O3) spacer layer on aluminum (Al) substrate has been proposed to enhance the absorption for two-dimensional (2D) materials. By combining dielectric array with metal substrate, the structure achieves multiple absorption peaks with near unity absorbance at near-infrared wavelengths due to the resonant effect of dielectric array. Completed monolayer graphene is utilized in the design without any demand of manufacture process to form the periodic patterns. Further analysis indicates that the near-field enhancement induced by surface modes gives rise to the high absorption. This favorable field enhancement and tunability of absorption not only open up new approaches to accelerate the light-graphene interaction, but also show great potential for practical applications in high-performance optoelectronic devices, such as modulators and sensors.

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;.

Far-infrared spectroscopic study of CeO2 nanocrystals

Science.gov (United States)

Popović, Z. V.; Grujić-Brojčin, M.; Paunović, N.; Radonjić, M. M.; Araújo, V. D.; Bernardi, M. I. B.; de Lima, M. M.; Cantarero, A.

2015-01-01

We present the far-infrared reflectivity spectra of 5 nm-sized pure and copper-doped Ce1- x Cu x O2- y ( x = 0; 0.01 and 0.10) nanocrystals measured at room temperature in the 50-650 cm-1 spectral range. Reflectivity spectra were analyzed using the factorized form of the dielectric function, which includes the phonon and the free carriers contribution. Four oscillators with TO energies of approximately 135, 280, 370, and 490 cm-1 were included in the fitting procedure. These oscillators represent local maxima of the CeO2 phonon density of states, which is also calculated using the density functional theory. The lowest energy oscillator represents TA(L)/TA(X) phonon states, which become infrared-active E u modes at the L and X points of the Brillouin zone (BZ). The second oscillator originates from TO(Γ) phonon states. The oscillator at 400 cm-1 originates from Raman mode phonon states, which at the L point of BZ also becomes infrared-active E u mode. The last oscillator describes phonons with dominantly LO(Γ) infrared mode character. The appearance of phonon density of states related oscillators, instead of single F 2uinfrared-active mode in the far-infrared reflectivity spectra, is a consequence of the nanosized dimension of the CeO2 particles. The best fit spectra are obtained using the generalized Bruggeman model for inhomogeneous media, which takes into account the nanocrystal volume fraction and the pore shape.

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

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

Non-thermal near-infrared exposure photobiomodulates cellular responses to ionizing radiation in human full thickness skin models.

Science.gov (United States)

König, Anke; Zöller, Nadja; Kippenberger, Stefan; Bernd, August; Kaufmann, Roland; Layer, Paul G; Heselich, Anja

2018-01-01

Ionizing and near-infrared radiation are both part of the therapeutic spectrum in cancer treatment. During cancer therapy ionizing radiation is typically used for non-invasive reduction of malignant tissue, while near-infrared photobiomodulation is utilized in palliative medical approaches, e.g. for pain reduction or impairment of wound healing. Furthermore, near-infrared is part of the solar wavelength spectrum. A combined exposure of these two irradiation qualities - either intentionally during medical treatment or unintentionally due to solar exposure - is therefore presumable for cancer patients. Several studies in different model organisms and cell cultures show a strong impact of near-infrared pretreatment on ionizing radiation-induced stress response. To investigate the risks of non-thermal near-infrared (NIR) pretreatment in patients, a human in vitro full thickness skin models (FTSM) was evaluated for radiation research. FTSM were pretreated with therapy-relevant doses of NIR followed by X-radiation, and then examined for DNA-double-strand break (DSB) repair, cell proliferation and apoptosis. Double-treated FTSM revealed a clear influence of NIR on X-radiation-induced stress responses in cells in their typical tissue environment. Furthermore, over a 24h time period, double-treated FTSM presented a significant persistence of DSBs, as compared to samples exclusively irradiated by X-rays. In addition, NIR pretreatment inhibited apoptosis induction of integrated fibroblasts, and counteracted the radiation-induced proliferation inhibition of basal keratinocytes. Our work suggests that cancer patients treated with X-rays should be prevented from uncontrolled NIR irradiation. On the other hand, controlled double-treatment could provide an alternative therapy approach, exposing the patient to less radiation. Copyright © 2017. Published by Elsevier B.V.

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 ...

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.

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.

Influence of the Dielectric Medium on the Carbonyl Infrared Absorption Peak of Acetylferrocene

Directory of Open Access Journals (Sweden)

F. López-Linares

2005-02-01

Full Text Available The solvent effect on the position of the carbonyl vibrational stretching ofacetylferrocene in aprotic media was studied in this work. The solvent-induced shifts in thisorganometallic compound were interpreted in terms of the alternative reaction field model(SCRF-MO proposed by Kolling. In contrast to the established trends for carbonyl groupsin organic systems, the results suggest that the continuum models for the reaction field arenot adequate and that the influence of dipolarity-polarizability described by aninhomogeneous coupling function θ (ε L(n 2 that assumes optical dielectric saturation isresponsible for the carbonyl band shift and, there is empirical evidence that the effect offield-induced intermolecular interaction on band shift, interpreted in terms of the van derWaals forces from the solvent, have a important contribution to this phenomena.

Multivariate calibration applied to the quantitative analysis of infrared spectra

Energy Technology Data Exchange (ETDEWEB)

Haaland, D.M.

1991-01-01

Multivariate calibration methods are very useful for improving the precision, accuracy, and reliability of quantitative spectral analyses. Spectroscopists can more effectively use these sophisticated statistical tools if they have a qualitative understanding of the techniques involved. A qualitative picture of the factor analysis multivariate calibration methods of partial least squares (PLS) and principal component regression (PCR) is presented using infrared calibrations based upon spectra of phosphosilicate glass thin films on silicon wafers. Comparisons of the relative prediction abilities of four different multivariate calibration methods are given based on Monte Carlo simulations of spectral calibration and prediction data. The success of multivariate spectral calibrations is demonstrated for several quantitative infrared studies. The infrared absorption and emission spectra of thin-film dielectrics used in the manufacture of microelectronic devices demonstrate rapid, nondestructive at-line and in-situ analyses using PLS calibrations. Finally, the application of multivariate spectral calibrations to reagentless analysis of blood is presented. We have found that the determination of glucose in whole blood taken from diabetics can be precisely monitored from the PLS calibration of either mind- or near-infrared spectra of the blood. Progress toward the non-invasive determination of glucose levels in diabetics is an ultimate goal of this research. 13 refs., 4 figs.

Quartz substrate infrared photonic crystal

Science.gov (United States)

Ghadiri, Khosrow; Rejeb, Jalel; Vitchev, Vladimir N.

2003-01-01

This paper presents the fabrication of a planar photonic crystal (p2c) made of a square array of dielectric rods embedded in air, operating in the infrared spectrum. A quartz substrate is employed instead of the commonly used silicon or column III-V substrate. Our square structure has a normalized cylinder radius-to-pitch ratio of r/a = 0.248 and dielectric material contrast ɛr of 4.5. We choose a Z-cut synthetic quartz for its cut (geometry), and etching properties. Then a particular Z-axis etching process is employed in order to ensure the sharp-edged verticality of the rods and fast etching speed. We also present the computer simulations that allowed the establishment of the photonic band gaps (PBG) of our photonic crystal, as well as the actual measurements. An experimental measurement have been carried out and compared with different simulations. It was found that experimental results are in good agreement with different simulation results. Finally, a frequency selective device for optical communication based on the introduction of impurity sites in the photonic crystal is presented. With our proposed structure Optical System on a Chip (OsoC) with micro-cavity based active devices such as lasers, diodes, modulators, couplers, frequency selective emitters, add-drop filters, detectors, mux/demuxes and polarizers connected by passive waveguide links can be realized.

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.

Ultrasensitive terahertz/infrared waveguide modulators based on multilayer graphene metamaterials

DEFF Research Database (Denmark)

Khromova, Irina; Andryieuski, Andrei; Lavrinenko, Andrei

2014-01-01

This paper studies and classifies the electromagnetic regimes of multilayer graphene-dielectric artificial metamate- rials in the terahertz/infrared range. The employment of such composites for waveguide-integrated modulators is analysed and three examples of novel tunable devices are presented. ...... leads to > 13 . 2 dB modulation depth. The third one is a tunable waveguide-based passband filter. The narrow-band cut-off con- ditions around the ON-state allow the latter to shift its central frequency by 1 . 25% per every meV graphene’s Fermi energy change...

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

Infrared optical constants, dielectric constants, molar polarizabilities, transition moments, dipole moment derivatives and Raman spectrum of liquid cyclohexane

Science.gov (United States)

Keefe, C. Dale; Pickup, Janet E.

2009-06-01

Previous studies have been done in this laboratory focusing on the optical properties of several liquid aromatic and aliphatic hydrocarbons in the infrared. The current study reports the infrared and absorption Raman spectra of liquid cyclohexane. Infrared spectra were recorded at 25 °C over a wavenumber range of 7400-490 cm -1. Infrared measurements were taken using transmission cells with pathlengths ranging from 3 to 5000 μm. Raman spectra were recorded between 3700 and 100 cm -1 at 25 °C using a 180° reflection geometry. Ab initio calculations of the vibrational wavenumbers at the B3LYP/6311G level of theory were performed and used to help assign the observed IR and Raman spectra. Extensive assignments of the fundamentals and binary combinations observed in the infrared imaginary molar polarizability spectrum are reported. The imaginary molar polarizability spectrum was curve fitted to separate the intensity from the various transitions and used to determine the transition moments and magnitudes of the derivatives of the dipole moment with respect to the normal coordinates for the fundamentals.

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)

Facile synthesis, dielectric properties and electrocatalytic activities of PMMA-NiFe{sub 2}O{sub 4} nanocomposite

Energy Technology Data Exchange (ETDEWEB)

Maji, Pranabi; Choudhary, Ram Bilash, E-mail: rbcism@gmail.com

2017-06-01

The paper deals with the dielectric and catalytic properties of poly (methyl methacrylate)-nikel ferrite (PMMA-NiFe{sub 2}O{sub 4}) nanocomposite. The nanocomposite was prepared by using a general and facile synthesis strategy. Fourier transform infrared (FTIR) and X-ray diffraction (XRD) spectra confirmed the formation of PMMA-NiFe{sub 2}O{sub 4} nanocomposite. Field effect scanning electron microscopic (FESEM) and transmission electron microscopic (TEM) images revealed that NiFe{sub 2}O{sub 4} nanoparticles were uniformly distributed and were tightly adhered with PMMA matrix owing to surface modification with 3-methacryloyloxy propyl trimethoxy silane (KH-570). Thermal stability was enhanced by incorporation of NiFe{sub 2}O{sub 4} nanofillers. The nanocomposite showed high dielectric constant and low dielectric loss. The achieved dielectric and thermal property inferred the potential application of this material in energy storage and embedded electronics devices. Further, the as prepared nanocomposite also offered a remarkable electrochemical performance towards hydrogen peroxide (H{sub 2}O{sub 2}) sensing. - Highlights: • PMMA-NiFe{sub 2}O{sub 4} nanocomposite was synthesized via free radical polymerization. • The nanocomposite exhibited high value of dielectric constant (51) and tanδ (0.3). • Thermal stability of the PMMA matrix was improved by the incorporation of NiFe{sub 2}O{sub 4.} • The H{sub 2}O{sub 2} detection limit was estimated 44 μM when signal to noise (S/N) ration was 3. • The electrochemical sensitivity of H{sub 2}O{sub 2} was calculated 0.6727 μA mM{sup -1}.

Effects of ultrasonication and conventional mechanical homogenization processes on the structures and dielectric properties of BaTiO3 ceramics.

Science.gov (United States)

Akbas, Hatice Zehra; Aydin, Zeki; Yilmaz, Onur; Turgut, Selvin

2017-01-01

The effects of the homogenization process on the structures and dielectric properties of pure and Nb-doped BaTiO 3 ceramics have been investigated using an ultrasonic homogenization and conventional mechanical methods. The reagents were homogenized using an ultrasonic processor with high-intensity ultrasonic waves and using a compact mixer-shaker. The components and crystal types of the powders were determined by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. The complex permittivity (ε ' , ε″) and AC conductivity (σ') of the samples were analyzed in a wide frequency range of 20Hz to 2MHz at room temperature. The structures and dielectric properties of pure and Nb-doped BaTiO 3 ceramics strongly depend on the homogenization process in a solid-state reaction method. Using an ultrasonic processor with high-intensity ultrasonic waves based on acoustic cavitation phenomena can make a significant improvement in producing high-purity BaTiO 3 ceramics without carbonate impurities with a small dielectric loss. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of doping on the dielectric properties of cerium oxide in the microwave and far-infrared frequency range

Czech Academy of Sciences Publication Activity Database

Santha, N. I.; Sebastian, M. T.; Mohanan, P.; McN.Alford, N.; Sarma, K.; Pullar, R. C.; Kamba, Stanislav; Pashkin, Alexej; Samoukhina, Polina; Petzelt, Jan

2004-01-01

Roč. 87, č. 7 (2004), s. 1233-1237 ISSN 0002-7820 R&D Projects: GA ČR GA202/01/0612; GA AV ČR KSK1010104 Institutional research plan: CEZ:AV0Z1010914 Keywords : microwave cearmics * dielectric dispersion Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.710, year: 2004

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.

Polarization Converter with Controllable Birefringence Based on Hybrid All-Dielectric-Graphene Metasurface

Science.gov (United States)

Owiti, Edgar O.; Yang, Hanning; Liu, Peng; Ominde, Calvine F.; Sun, Xiudong

2018-02-01

Previous studies on hybrid dielectric-graphene metasurfaces have been used to implement induced transparency devices, while exhibiting high Q-factors based on trapped magnetic resonances. Typically, the transparency windows are single wavelength and less appropriate for polarization conversion structures. In this work, a quarter-wave plate based on a hybrid silicon-graphene metasurface with controllable birefringence is numerically designed. The phenomena of trapped magnetic mode resonance and high Q-factors are modulated by inserting graphene between silicon and silica. This results in a broader transmission wavelength in comparison to the all-dielectric structure without graphene. The birefringence tunability is based on the dimensions of silicon and the Fermi energy of graphene. Consequently, a linear-to-circular polarization conversion is achieved at a high degree of 96%, in the near-infrared. Moreover, the polarization state of the scattered light is switchable between right and left hand circular polarizations, based on an external gate biasing voltage. Unlike in plasmonic metasurfaces, these achievements demonstrate an efficient structure that is free from radiative and ohmic losses. Furthermore, the ultrathin thickness and the compactness of the structure are demonstrated as key components in realizing integrable and CMOS compatible photonic sensors.

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.

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.

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.

Dielectric Properties of Polyether Sulfone/Bismaleimide Resin Composite Based on Nanolumina Modified by Super-Critical Ethanol

Science.gov (United States)

Chen, Yufei; Li, Zhichao; Teng, Chengjun; Li, Fangliang; Han, Yang

2016-11-01

Nano-alumina was chemically modified with super-critical ethanol enabling a surface active coating. Modified nano-alumina was incorporated in polymer blends based on thermoplastic polyether sulfone and thermosetting bismaleimide resin to produce novel nanocomposites designated as SCE-Al2O3/PES-MBAE. In the SCE-Al2O3/PES-MBAE nano-composites, the matrix was originally formed from 4,4'-diamino diphenyl methane bismaleimide (MBMI) using the diluents of 3,3'-diallyl bisphenol A (BBA) and bisphenol-A diallyl ether (BBE), while polyether sulfone (PES) was used as toughening agent along with super-critically modified nano-alumina (SCE-Al2O3) as filler material. The content of SCE-Al2O3 was varied from 0 wt.% to 6 wt.%. The nano-composites were characterized for their morphological, spectroscopic and dielectric properties. Fourier transform infrared spectroscopy (FT-IR) indicated that ethanol molecules had adhered to the surface of the nano-Al2O3 in super-critical state. A reaction between MBMI and allyl compound occurred and SCE-Al2O3 was doped into the polymer matrix. Volume resistivity of the composite initially increased and then decreased. The modification due to SCE-Al2O3 could overcome the undesirable impact of PES by using a bare minimum level of SCE-Al2O3. The dielectric constant ( ɛ) and dielectric loss (tan δ) as in the case of volume resistivity were initially increased and then decreased with the content of SCE-Al2O3 in the composite. The dielectric constant, dielectric loss and dielectric strength of SCE-Al2O3 (4 wt.%)/PES (5 wt.%)-MBAE nano-composite were 3.53 (100 Hz), 1.52 × 10-3 (100 Hz) and 15.66 kV/mm, respectively, which indicated that the dielectric properties of the composite fulfilled the basic requirements of electrical and insulating material. It was evident from the morphological analysis that the SCE-Al2O3 was evenly dispersed at the nanoscale; for example, the size of SCE-Al2O3 in SCE-Al2O3 (4 wt.%)/PES (5 wt.%)-MBAE measured less than 50 nm.

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)

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.

Improvement of Mechanical and Dielectric Properties of Epoxy Resin Using CNTs/ZnO Nanocomposite.

Science.gov (United States)

Vu, Pham Gia; Truc, Trinh Anh; Chinh, Nguyen Thuy; Tham, Do Quang; Trung, Tran Huu; Oanh, Vu Ke; Hang, To Thi Xuan; Olivier, Marjorie; Hoang, Thai

2018-04-01

In this study, carbon nanotubes (CNTs)/ZnO composites had been prepared using the sol-gel method and then incorporated into an epoxy resin for reinforcement of mechanical and electrical properties. Fourier Transform Infrared (FTIR), X-ray diffraction (XRD) Field Emission Scanning Electron Microscope (FE-SEM) analyses show that the ZnO nanoparticles deposited on CNTs were crystallized in a hexagonal wurtzite structure. Average particle size of ZnO deposited on the CNT was about 8 nm. The mechanical and dielectric properties of epoxy containing CNTs/ZnO were investigated in comparison to epoxy resin and epoxy resin containing only CNT or ZnO nanoparticles. The results indicated that tensile strength and elongation at break of the nanocomposite were substantially improved with the presence of CNTs/ZnO at the equal volume. The DSC analysis associate with the dielectric results shows that the behavior of epoxy/CNTs/ZnO is identical to epoxy/ZnO composite, and the CNTs is essential to the distributed arrangement of ZnO in the epoxy resin.

Broadband Terahertz Refraction Index Dispersion and Loss of Polymeric Dielectric Substrate and Packaging Materials

Science.gov (United States)

Motaharifar, E.; Pierce, R. G.; Islam, R.; Henderson, R.; Hsu, J. W. P.; Lee, Mark

2018-01-01

In the effort to push the high-frequency performance of electronic circuits and signal interconnects from millimeter waves to beyond 1 THz, a quantitative knowledge of complex refraction index values and dispersion in potential dielectric substrate, encapsulation, waveguide, and packaging materials becomes critical. Here we present very broadband measurements of the real and imaginary index spectra of four polymeric dielectric materials considered for use in high-frequency electronics: benzocyclobutene (BCB), polyethylene naphthalate (PEN), the photoresist SU-8, and polydimethylsiloxane (PDMS). Reflectance and transmittance spectra from 3 to 75 THz were made using a Fourier transform spectrometer on freestanding material samples. These data were quantitatively analyzed, taking into account multiple partial reflections from front and back surfaces and molecular bond resonances, where applicable, to generate real and imaginary parts of the refraction index as a function of frequency. All materials showed signatures of infrared active organic molecular bond resonances between 10 and 50 THz. Low-loss transmission windows as well as anti-window bands of high dispersion and loss can be readily identified and incorporated into high-frequency design models.

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

Science.gov (United States)

Zhou, Xiaobing; Li, Shusun; Stamnes, Knut

2003-07-20

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

Infrared spectra of jennite and tobermorite from first-principles

Energy Technology Data Exchange (ETDEWEB)

Vidmer, Alexandre, E-mail: alexandre@vidmer.com; Sclauzero, Gabriele; Pasquarello, Alfredo

2014-06-01

The infrared absorption spectra of jennite, tobermorite 14 Å, anomalous tobermorite 11 Å, and normal tobermorite 11 Å are simulated within a density-functional-theory scheme. The atomic coordinates and the cell parameters are optimized resulting in structures which agree with previous studies. The vibrational frequencies and modes are obtained for each mineral. The vibrational density of states is analyzed through extensive projections on silicon tetrahedra, oxygen atoms, OH groups, and water molecules. The coupling with the electric field is achieved through the use of density functional perturbation theory, which yields Born effective charges and dielectric constants. The simulated absorption spectra reproduce well the experimental spectra, thereby allowing for a detailed interpretation of the spectral features in terms of the underlying vibrational modes. In the far-infrared part of the absorption spectra, the interplay between Ca and Si related vibrations leads to differences which are sensitive to the calcium/silicon ratio of the mineral.

Characterization of InSb layers on GaAs substrates using infrared reflectance and a modified oscillator formula

Energy Technology Data Exchange (ETDEWEB)

Engelbrecht, J.A.A., E-mail: Japie.Engelbrecht@nmmu.ac.z [Physics Department, Nelson Mandela Metropolitan University, Box 77000, Port Elizabeth 6031 (South Africa); Wagener, M.C. [Physics Department, Nelson Mandela Metropolitan University, Box 77000, Port Elizabeth 6031 (South Africa)

2009-12-01

InSb epilayers on GaAs substrates are analyzed using infrared reflectance spectroscopy, but employing a modified Drude oscillator formula. The modified formula enables the determination of 13 parameters: six dielectric parameters for both layer and substrate separately, as well as the thickness of the layer. The formula is tested against previously published data, and to characterize layers grown in this laboratory.

Characterization of InSb layers on GaAs substrates using infrared reflectance and a modified oscillator formula

International Nuclear Information System (INIS)

Engelbrecht, J.A.A.; Wagener, M.C.

2009-01-01

InSb epilayers on GaAs substrates are analyzed using infrared reflectance spectroscopy, but employing a modified Drude oscillator formula. The modified formula enables the determination of 13 parameters: six dielectric parameters for both layer and substrate separately, as well as the thickness of the layer. The formula is tested against previously published data, and to characterize layers grown in this laboratory.

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

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.

Adaptive infrared-reflecting systems inspired by cephalopods

Science.gov (United States)

Xu, Chengyi; Stiubianu, George T.; Gorodetsky, Alon A.

2018-03-01

Materials and systems that statically reflect radiation in the infrared region of the electromagnetic spectrum underpin the performance of many entrenched technologies, including building insulation, energy-conserving windows, spacecraft components, electronics shielding, container packaging, protective clothing, and camouflage platforms. The development of their adaptive variants, in which the infrared-reflecting properties dynamically change in response to external stimuli, has emerged as an important unmet scientific challenge. By drawing inspiration from cephalopod skin, we developed adaptive infrared-reflecting platforms that feature a simple actuation mechanism, low working temperature, tunable spectral range, weak angular dependence, fast response, stability to repeated cycling, amenability to patterning and multiplexing, autonomous operation, robust mechanical properties, and straightforward manufacturability. Our findings may open opportunities for infrared camouflage and other technologies that regulate infrared radiation.

Possible influence of surface oxides on the optical response of high-purity niobium material used in the fabrication of superconducting radio frequency cavity

Science.gov (United States)

Singh, Nageshwar; Deo, M. N.; Roy, S. B.

2016-09-01

We have investigated the possible influence of surface oxides on the optical properties of a high-purity niobium (Nb) material for fabrication of superconducting radio frequency (SCRF) cavities. Various peaks in the infrared region were identified using Fourier transform infrared and Raman spectroscopy. Optical response functions such as complex refractive index, dielectric and conductivity of niobium were compared with the existing results on oxides free Nb and Cu. It was observed that the presence of a mixture of niobium-oxides, and probably near other surface impurities, appreciably influence the conducting properties of the material causing deviation from the typical metallic characteristics. In this way, the key result of this work is the observation, identification of vibrational modes of some of surface complexes and study of its influences on the optical responses of materials. This method of spectroscopic investigation will help in understanding the origin of degradation of performance of SCRF cavities.

Possible influence of surface oxides on the optical response of high-purity niobium material used in the fabrication of superconducting radio frequency cavity

International Nuclear Information System (INIS)

Singh, Nageshwar; Deo, M.N.; Roy, S.B.

2016-01-01

We have investigated the possible influence of surface oxides on the optical properties of a high-purity niobium (Nb) material for fabrication of superconducting radio frequency (SCRF) cavities. Various peaks in the infrared region were identified using Fourier transform infrared and Raman spectroscopy. Optical response functions such as complex refractive index, dielectric and conductivity of niobium were compared with the existing results on oxides free Nb and Cu. It was observed that the presence of a mixture of niobium-oxides, and probably near other surface impurities, appreciably influence the conducting properties of the material causing deviation from the typical metallic characteristics. In this way, the key result of this work is the observation, identification of vibrational modes of some of surface complexes and study of its influences on the optical responses of materials. This method of spectroscopic investigation will help in understanding the origin of degradation of performance of SCRF cavities.

Possible influence of surface oxides on the optical response of high-purity niobium material used in the fabrication of superconducting radio frequency cavity

Energy Technology Data Exchange (ETDEWEB)

Singh, Nageshwar [Magnetic and Superconducting Materials Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, M.P. (India); Deo, M.N. [High Pressure & Synchrotron Radiation Physics Division, BARC, Mumbai 400085 (India); Roy, S.B. [Magnetic and Superconducting Materials Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, M.P. (India)

2016-09-11

We have investigated the possible influence of surface oxides on the optical properties of a high-purity niobium (Nb) material for fabrication of superconducting radio frequency (SCRF) cavities. Various peaks in the infrared region were identified using Fourier transform infrared and Raman spectroscopy. Optical response functions such as complex refractive index, dielectric and conductivity of niobium were compared with the existing results on oxides free Nb and Cu. It was observed that the presence of a mixture of niobium-oxides, and probably near other surface impurities, appreciably influence the conducting properties of the material causing deviation from the typical metallic characteristics. In this way, the key result of this work is the observation, identification of vibrational modes of some of surface complexes and study of its influences on the optical responses of materials. This method of spectroscopic investigation will help in understanding the origin of degradation of performance of SCRF cavities.

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.

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....

A noninvasive brain computer interface using visually-induced near-infrared spectroscopy responses.

Science.gov (United States)

Chen, Cheng-Hsuan; Ho, Ming-Shan; Shyu, Kuo-Kai; Hsu, Kou-Cheng; Wang, Kuo-Wei; Lee, Po-Lei

2014-09-19

Visually-induced near-infrared spectroscopy (NIRS) response was utilized to design a brain computer interface (BCI) system. Four circular checkerboards driven by distinct flickering sequences were displayed on a LCD screen as visual stimuli to induce subjects' NIRS responses. Each flickering sequence was a concatenated sequence of alternative flickering segments and resting segments. The flickering segment was designed with fixed duration of 3s whereas the resting segment was chosen randomly within 15-20s to create the mutual independencies among different flickering sequences. Six subjects were recruited in this study and subjects were requested to gaze at the four visual stimuli one-after-one in a random order. Since visual responses in human brain are time-locked to the onsets of visual stimuli and the flicker sequences of distinct visual stimuli were designed mutually independent, the NIRS responses induced by user's gazed targets can be discerned from non-gazed targets by applying a simple averaging process. The accuracies for the six subjects were higher than 90% after 10 or more epochs being averaged. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Standard reference for instrument response function in fluorescence lifetime measurements in visible and near infrared

International Nuclear Information System (INIS)

Chib, Rahul; Shah, Sunil; Gryczynski, Zygmunt; Fudala, Rafal; Borejdo, Julian; Gryczynski, Ignacy; Zelent, Bogumil; Corradini, Maria G; Ludescher, Richard D

2016-01-01

Allura red (AR) fluorophore, a common dye in the food industry, displays a broad emission spectrum in water (visible-to-near infrared region of the electromagnetic spectrum) and has a remarkably short fluorescence lifetime of about 10 ps. This short lifetime does not depend on the emission (observation) wavelength. We examined time responses of AR fluorescence across emission wavelengths from 550 nm to 750 nm and found that it is an ideal candidate for impulse response functions in fluorescence lifetime measurements. (technical note)

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.

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...

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.

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.

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

Infrared and millimeter waves v.15 millimeter components and techniques, pt.VI

CERN Document Server

Button, Kenneth J

1986-01-01

Infrared and Millimeter Waves, Volume 15: Millimeter Components and Techniques, Part VI is concerned with millimeter-wave guided propagation and integrated circuits. This book covers low-noise receiver technology for near-millimeter wavelengths; dielectric image-line antennas; EHF satellite communications (SATCOM) terminal antennas; and semiconductor antennas for millimeter-wave integrated circuits. A scanning airborne radiometer for 30 and 90 GHz and a self-oscillating mixer are also described. This monograph is comprised of six chapters and begins with a discussion on the design of low-n

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

Structural, optical, dielectric and magnetic studies of gadolinium-added Mn-Cu nanoferrites

Science.gov (United States)

Kanna, R. Rajesh; Lenin, N.; Sakthipandi, K.; Kumar, A. Senthil

2018-05-01

Spinel ferrite with the general formula Mn1-xCuxFe1.85Gd0.15O4 (x = 0.2, 0.4, 0.6 and 0.8) was synthesized using the standard sonochemical method. The structure, optical, morphology, dielectric and magnetic properties of the prepared Mn1-xCuxFe1.85Gd0.15O4 nanoferrites were exhaustively investigated using various characterization techniques. The phase purity, secondary phase and crystallite parameters were studied from X-ray diffraction patterns. Fourier transform infrared spectra showed two absorption bands of transition metal oxides in the frequency range from 400 to 650 cm-1, which are related to asymmetric stretching modes of the spinel ferrites (AB2O4). Raman spectra have five active modes illustrating the vibration of O2- ions at both tetrahedral (A) site and octahedral (B) site ions. The wide and narrow scan spectrum from X-ray photoelectron spectroscopy results confirmed the presence of Mn, Cu, Gd, Fe, C and O elements in the composition. The oxidation state and core level of the photo electron peaks of Mn 2p, Cu 2p, Gd 3d, Fe 2p and O 1s were analyzed. The influence of the Cu2+ concentration in Mn1-xCuxFe1.85Gd0.15O4 on the morphology, varying from nanorods, nanoflakes to spherical, was explored on the basis of scanning electron microscopy images. Ultraviolet diffuse reflectance spectroscopy studies indicated that the optical bandgap (5.12-5.32 eV) of the nanoferrites showed an insulating behavior. The dielectric constant, loss tangent and complex dielectric constant values decreased with an increase in frequency with the addition of Gd3+ content. A vibrating sample magnetometer showed that the prepared nanoferrites had a soft ferromagnetic nature. The magnetic parameter changed markedly with an increase in the Cu content in Mn1-xCuxFe1.85Gd0.15O4 nanoferrites. The optical, dielectric and magnetic properties were considerably enhanced with the addition of Gd3+ ions in the spinel nanoferrites.

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.

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.

Physiological response of Arundo donax to cadmium stress by Fourier transform infrared spectroscopy

Science.gov (United States)

Yu, Shunhui; Sheng, Li; Zhang, Chunyan; Deng, Hongping

2018-06-01

The present paper deals with the physiological response of the changes in chemical contents of the root, stem and leaf of Arundo donax seedlings stressed by excess cadmium using Fourier transform infrared spectroscopy technique, cadmium accumulation in plant by atomic absorption spectroscopy were tested after different concentrations cadmium stress. The results showed that low cadmium concentrations (spectroscopy technique for the non-invasive and rapid monitoring of the plants stressed with heavy metals, Arundo donax is suitable for phytoremediation of cadmium -contaminated wetland.

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.

Graphene oxide reinforced poly (4-styrenesulfonic acid)/polyvinyl alcohol blend composites with enhanced dielectric properties for portable and flexible electronics

Energy Technology Data Exchange (ETDEWEB)

Deshmukh, Kalim, E-mail: deshmukh.kalim@gmail.com [Department of Physics, B.S. Abdur Rahman University, Chennai, 600048, TN (India); Ahamed, M. Basheer [Department of Physics, B.S. Abdur Rahman University, Chennai, 600048, TN (India); Sadasivuni, Kishor Kumar [Mechanical and Industrial Engineering Department, Qatar University, P.O. Box 2713, Doha (Qatar); Ponnamma, Deepalekshmi; AlMaadeed, Mariam Al-Ali [Center for Advanced Materials, Qatar University, P.O. Box 2713, Doha (Qatar); Khadheer Pasha, S.K. [Department of Physics, School of Advanced Sciences, VIT University, Vellore, 632014, TN (India); Deshmukh, Rajendra R. [Department of Physics, Institute of Chemical Technology, Matunga, Mumbai, 400019 (India); Chidambaram, K. [Department of Physics, School of Advanced Sciences, VIT University, Vellore, 632014, TN (India)

2017-01-15

In this work, Graphene Oxide (GO) reinforced novel polymer composites comprising of poly (4-styrenesulfonic acid) (PSSA) and polyvinyl alcohol (PVA) blend matrix have been developed using colloidal processing technique. The properties and the structure of prepared composites were investigated using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), UV–vis spectroscopy (UV), Thermogravimetric analysis (TGA), Polarized optical microscopy (POM), Scanning electron microscopy (SEM) and Atomic force microscopy (AFM). The FTIR and Raman spectroscopy analysis indicate the strong interfacial interaction between GO and PSSA/PVA blend matrix. The XRD and SEM analysis confirm that GO was fully exfoliated into individual graphene sheets and dispersed homogeneously within the polymer matrix. The effective reinforcement of GO into PSSA/PVA blend matrix has resulted in the enhancement of dielectric constant. The dielectric constant has increased from 82.67 (50 Hz, 150 °C) for PSSA/PVA (50/50) blend to 297.91 (50 Hz, 150 °C) for PSSA/PVA/GO composites with 3 wt % GO loading. The dielectric loss (tan δ) has increased from 1.56 (50 KHz, 140 °C) for PSSA/PVA (50/50) blend to 2.64 (50 KHz, 140 °C) for PSSA/PVA/GO composites with 3 wt % GO loading. These findings provide a new insight to fabricate flexible, high-k dielectric composite as a promising material for energy storage applications. - Highlights: • Graphene Oxide was prepared from natural graphite using modified Hummers method. • Novel PSSA/PVA/GO composites were prepared by reinforcing GO into PSSA/PVA blend matrix. • Molecular level dispersion of GO in PSSA/PVA blend matrix was successfully achieved. • Enhancement in the dielectric constant was observed due to effective reinforcement of GO in PSSA/PVA blend matrix. • PSSA/PVA/GO composites with high dielectric performances can be considered for energy storage applications.

Aging phenomena of chitosan and chitosan-diclofenac sodium system detected by low-frequency dielectric spectroscopy.

Science.gov (United States)

Bodek, K H; Bak, G W

1999-09-01

The use of natural polymers for design of dosage form has received considerable attention recently, especially from the safety point of view. Among these polymers, chitosan shows very interesting biological, chemical and physical properties which makes it possible to use chitosan for various pharmaceutical applications. Microcrystalline chitosan (MCCh) is a special multifunctional polymeric material existing in the form of either of gelatinous water dispersion or a powder. Thermal aging of chitosan and chitosan-diclofenac sodium mixture have been studied using low-frequency dielectric measurements. The aging was carried out by annealing in ambient atmosphere in the temperature range between 25 degrees C and 100 degrees C. The dielectric losses in the aged samples proved to decrease by about one order of magnitude. The additional measurements of molecular weight distribution and infrared absorption were also carried out for better understanding of nature of the ageing phenomena. Partial evacuation of water, cross-linking and improvement of structural order may be suggested to be a result of thermal aging of the investigated materials.

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...

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.

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.

Far-infrared spectroscopic study of CeO{sub 2} nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Popović, Z. V., E-mail: zoran.popovic@ipb.ac.rs; Grujić-Brojčin, M.; Paunović, N. [University of Belgrade, Center for Solid State Physics and New Materials, Institute of Physics (Serbia); Radonjić, M. M. [University of Belgrade, Scientific Computing Laboratory, Institute of Physics Belgrade (Serbia); Araújo, V. D.; Bernardi, M. I. B. [Universidade de São Paulo-USP, Instituto de Fisica (Brazil); Lima, M. M. de; Cantarero, A. [Universidad de Valencia, Instituto de Ciencia de Los Materiales (Spain)

2015-01-15

We present the far-infrared reflectivity spectra of 5 nm-sized pure and copper-doped Ce{sub 1−x}Cu{sub x}O{sub 2−y} (x = 0; 0.01 and 0.10) nanocrystals measured at room temperature in the 50–650 cm{sup −1} spectral range. Reflectivity spectra were analyzed using the factorized form of the dielectric function, which includes the phonon and the free carriers contribution. Four oscillators with TO energies of approximately 135, 280, 370, and 490 cm{sup −1} were included in the fitting procedure. These oscillators represent local maxima of the CeO{sub 2} phonon density of states, which is also calculated using the density functional theory. The lowest energy oscillator represents TA(L)/TA(X) phonon states, which become infrared-active E{sub u} modes at the L and X points of the Brillouin zone (BZ). The second oscillator originates from TO(Γ) phonon states. The oscillator at ∼400 cm{sup −1} originates from Raman mode phonon states, which at the L point of BZ also becomes infrared-active E{sub u} mode. The last oscillator describes phonons with dominantly LO(Γ) infrared mode character. The appearance of phonon density of states related oscillators, instead of single F{sub 2u}infrared-active mode in the far-infrared reflectivity spectra, is a consequence of the nanosized dimension of the CeO{sub 2} particles. The best fit spectra are obtained using the generalized Bruggeman model for inhomogeneous media, which takes into account the nanocrystal volume fraction and the pore shape.

Infrared dispersion analysis and Raman scattering spectra of taurine single crystals

Science.gov (United States)

Moreira, Roberto L.; Lobo, Ricardo P. S. M.; Dias, Anderson

2018-01-01

A comprehensive set of optical vibrational modes of monoclinic taurine crystals was determined by Raman scattering, and infrared reflectivity and transmission spectroscopies. By using appropriate scattering/reflection geometries, the vibrational modes were resolved by polarization and the most relevant modes of the crystal could be assigned. In particular, we were able to review the symmetry of the gerade modes and to resolve ambiguities in the literature. Owing to the non-orthogonal character of Bu modes in monoclinic crystals (lying on the optic axial plane), we carried out a generalized Lorentz dispersion analysis consisting of simultaneous adjust of infrared-reflectivity spectra at various light polarization angles. The Au modes (parallel to the C2-axis) were treated within the classical Lorentz model. The behavior of off-diagonal and diagonal terms of the complex dielectric tensors and the presence of anomalous dispersion were discussed as consequences of the low symmetry of the crystal.

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.

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.

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.

Large-scale modulation of left-handed passband in hybrid graphene/dielectric metasurface

Energy Technology Data Exchange (ETDEWEB)

Liu, Chuanbao; Bai, Yang; Qiao, Lijie [Key Laboratory of Environmental Fracture (Ministry of Education), University of Science and Technology Beijing (China); Zhou, Ji [State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing (China); Zhao, Qian [State Kay Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing (China)

2017-08-15

Large-scale modulation of the left-handed transmission with a high quality factor is greatly desired by high-performance optical devices, but the requirements are hard to be satisfied simultaneously. This paper presents a hybrid graphene/dielectric metasurface to realize a large transmission modulation for the left-handed passband at near-infrared frequencies via tuning the Fermi energy of graphene. By splitting the nanoblocks, i.e. introducing an additional symmetry breaking in the unit cell, the metasurface demonstrates an ultrahigh quality factor (Q ∼ 550) of Fano resonance with near-unity transmission and full 2π phase coverage due to the interference between Mie-type magnetic and electric resonances, which induces the negative refraction property. Besides, the split in the nanoblock greatly enhances the local field by increasing the critical coupling area, so the light-graphene interaction is promoted intensively. When the surface conductivity of graphene is electrically tuned, the hybrid graphene/dielectric metasurface exhibits a deep modulation of 85% for the left-handed passband, which is robust even for the highest loss of graphene. Moreover, the simple configuration remarkably reduces the fabrication requirements to facilitate the widespread applications. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Influence of Chemical Composition and Structure in Silicon Dielectric Materials on Passivation of Thin Crystalline Silicon on Glass.

Science.gov (United States)

Calnan, Sonya; Gabriel, Onno; Rothert, Inga; Werth, Matteo; Ring, Sven; Stannowski, Bernd; Schlatmann, Rutger

2015-09-02

In this study, various silicon dielectric films, namely, a-SiOx:H, a-SiNx:H, and a-SiOxNy:H, grown by plasma enhanced chemical vapor deposition (PECVD) were evaluated for use as interlayers (ILs) between crystalline silicon and glass. Chemical bonding analysis using Fourier transform infrared spectroscopy showed that high values of oxidant gases (CO2 and/or N2), added to SiH4 during PECVD, reduced the Si-H and N-H bond density in the silicon dielectrics. Various three layer stacks combining the silicon dielectric materials were designed to minimize optical losses between silicon and glass in rear side contacted heterojunction pn test cells. The PECVD grown silicon dielectrics retained their functionality despite being subjected to harsh subsequent processing such as crystallization of the silicon at 1414 °C or above. High values of short circuit current density (Jsc; without additional hydrogen passivation) required a high density of Si-H bonds and for the nitrogen containing films, additionally, a high N-H bond density. Concurrently high values of both Jsc and open circuit voltage Voc were only observed when [Si-H] was equal to or exceeded [N-H]. Generally, Voc correlated with a high density of [Si-H] bonds in the silicon dielectric; otherwise, additional hydrogen passivation using an active plasma process was required. The highest Voc ∼ 560 mV, for a silicon acceptor concentration of about 10(16) cm(-3), was observed for stacks where an a-SiOxNy:H film was adjacent to the silicon. Regardless of the cell absorber thickness, field effect passivation of the buried silicon surface by the silicon dielectric was mandatory for efficient collection of carriers generated from short wavelength light (in the vicinity of the glass-Si interface). However, additional hydrogen passivation was obligatory for an increased diffusion length of the photogenerated carriers and thus Jsc in solar cells with thicker absorbers.

Temperature responsive porous silicon nanoparticles for cancer therapy - spatiotemporal triggering through infrared and radiofrequency electromagnetic heating.

Science.gov (United States)

Tamarov, Konstantin; Xu, Wujun; Osminkina, Liubov; Zinovyev, Sergey; Soininen, Pasi; Kudryavtsev, Andrey; Gongalsky, Maxim; Gaydarova, Azha; Närvänen, Ale; Timoshenko, Victor; Lehto, Vesa-Pekka

2016-11-10

One critical functionality of the carrier system utilized in targeted drug delivery is its ability to trigger the release of the therapeutic cargo once the carrier has reached its target. External triggering is an alluring approach as it can be applied in a precise spatiotemporal manner. In the present study, we achieved external triggering through the porous silicon (PSi) nanoparticles (NPs) by providing a pulse of infrared or radiofrequency radiation. The NPs were grafted with a temperature responsive polymer whose critical temperature was tailored to be slightly above 37°C. The polymer coating improved the biocompatibility of the NPs significantly in comparison with their uncoated counterparts. Radiation induced a rapid temperature rise, which resulted in the collapse of the polymer chains facilitating the cargo release. Both infrared and radiofrequency radiation were able to efficiently trigger the release of the encapsulated drug in vitro and induce significant cell death in comparison to the control groups. Radiofrequency radiation was found to be more efficient in vitro, and the treatment efficacy was verified in vivo in a lung carcinoma (3LL) mice model. After a single intratumoral administration of the carrier system combined with radiofrequency radiation, there was clear suppression of the growth of the carcinoma and a prolongation of the survival time of the animals. The temperature responsive (TR) polymer grafted on the surface of porous silicon nanoparticles (PSi NPs) changes its conformation in response to the heating induced by infrared or radiofrequency radiation. The conformation change allows the loaded doxorubicin to escape from the pores, achieving controlled drug release from TR PSi NPs, which displayed efficacy against malignant cells both in vitro and in vivo. Copyright © 2016 Elsevier B.V. All rights reserved.

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

A Micromachined Infrared Senor for an Infrared Focal Plane Array

Directory of Open Access Journals (Sweden)

Seong M. Cho

2008-04-01

Full Text Available A micromachined infrared sensor for an infrared focal plane array has been designed and fabricated. Amorphous silicon was used as a sensing material, and silicon nitride was used as a membrane material. To get a good absorption in infrared range, the sensor structure was designed as a l/4 cavity structure. A Ni-Cr film was selected as an electrode material and mixed etching scheme was applied in the patterning process of the Ni-Cr electrode. All the processes were made in 0.5 μm iMEMS fabricated in the Electronics and Telecommunication Research Institute (ETRI. The processed MEMS sensor had a small membrane deflection less than 0.15 μm. This small deflection can be attributed to the rigorous balancing of the stresses of individual layers. The efficiency of infrared absorption was more than 75% in the wavelength range of 8 ~ 14 μm. The processed infrared sensor showed high responsivity of ~230 kV/W at 1.0V bias and 2 Hz operation condition. The time constant of the sensor was 8.6 msec, which means that the sensor is suitable to be operated in 30 Hz frame rate.

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

Terahertz response of two-dimensional charge carrier systems in GaAs-based heterostructures; Terahertz-Antwort von zweidimensionalen Ladungstraegersystemen in GaAs-basierten Heterostrukturen

Energy Technology Data Exchange (ETDEWEB)

Grunwald, Torben

2009-12-17

This thesis deals with the THz response of two-dimensional charge carrier systems in different semiconductor heterostructures under varying conditions. The utilized spectrometer is suitable for time-resolved optical pump - THz probe experiments, as well as for optical pump-probe experiments in the near infrared for identical conditions. It allows the investigation of the transverse dielectric function of both, a (GaIn)As/GaAs quantum well and a two-dimensional electron gas in a GaAs-based heterostructure. First, the THz response of an electron-hole plasma is examined for different carrier densities. The plasma is generated by interband transitions in a (GaIn)As/GaAs quantum well. The measured transverse dielectric function reveals that the plasma behaves in accordance with the classical Drude oscillator model. It also conforms to the microscopic theory of the THz response of corresponding many-body systems. Evidence of a plasma resonance in the negative imaginary part of the inverse dielectric function is found. The squared peak frequency of the resonance is proportional to the carrier density of the plasma. This behavior corresponds to the plasma frequency of a three-dimensional plasma. Overall, it can be shown that the transverse THz response of a two-dimensional electron-hole plasma behaves like the response of a three-dimensional plasma. Therefore, the transversal THz response of an electron-hole plasma seems to be independent of the dimension of the charge carrier system. Secondly, the behavior of the quantum well for a 1s-exciton dominated carrier system is investigated. A good agreement between experiment and microscopic theory is obtained for the dielectric function. The negative imaginary part of the inverse dielectric function shows a resonance at the intraexcitonic 1s-2p transition frequency, even in weakly excited excitonic systems. Increasing the carrier density leads to a plasma-like behavior of the system. However, in these densities a significant

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.

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.

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.

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.

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.

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.

Trans-cranial infrared laser stimulation induces hemodynamic and metabolic response measured by broadband near infrared spectroscopy in vivo on human forehead (Conference Presentation)

Science.gov (United States)

Wang, Xinlong; Nalawade, Sahil Sunil; Reddy, Divya Dhandapani; Tian, Fenghua; Gonzalez-Lima, F.; Liu, Hanli

2017-02-01

Transcranial infrared laser stimulation (TILS) uses infrared light (lasers or LEDs) for nondestructive and non-thermal photobiomodulation on the human brain. Although TILS has shown its beneficial effects to a variety of neurological and psychological conditions, its physiological mechanism remains unknown. Cytochrome-c-oxidase (CCO), the last enzyme in the electron transportation chain, is proposed to be the primary photoacceptor of this infrared laser. In this study, we wish to validate this proposed mechanism. We applied 8 minutes in vivo TILS on the right forehead of 11 human participants with a 1064-nm laser. Broad-band near infrared spectroscopy (bb-NIRS) from 740-900nm was also employed near the TILS site to monitor hemodynamic and metabolic responses during the stimulation and 5-minute recovery period. For rigorous comparison, we also performed similar 8-min bb-NIR measurements under placebo conditions. A multi-linear regression analysis based on the modified Beer-Lambert law was performed to estimate concentration changes of oxy-hemoglobin (Δ[HbO]), deoxy-hemoglobin (Δ[Hb]), and cytochrome-c-oxidase (Δ[CCO]). We found that TILS induced significant increases of [CCO], [HbO] and a decrease of [Hb] with dose-dependent manner as compared with placebo treatments. Furthermore, strong linear relationships or interplays between [CCO] versus [HbO] and [CCO] versus [Hb] induced by TILS were observed in vivo for the first time. These relationships have clearly revealed close coupling/relationship between the hemodynamic oxygen supply and blood volume versus up-regulation of CCO induced by photobiomodulation. Our results demonstrate the tremendous potential of bb-NIRS as a non-invasive in vivo means to study photobiomodulation mechanisms and perform treatment evaluations of TILS.

Influence of calcination temperature on sol-gel synthesized single-phase bismuth titanate for high dielectric capacitor applications

Energy Technology Data Exchange (ETDEWEB)

Thiruramanathan, Pandirengan; Marikani, Arumugam [Mepco Schlenk Engineering College, Tamil Nadu (India). Dept. of Physics; Madhavan, Durairaj [Mepco Schlenk Engineering College, Tamil Nadu (India). Dept. of Chemistry; Bharadwaj, Suresh; Awasthi, Anand Mohan [UGC-DAE Consortium for Scientific Research, Indore (India). Thermodynamics Lab.

2016-05-15

An inexpensive sol-gel combustion method using citric acid as fuel has been used to synthesize bismuth titanate, Bi{sub 4}Ti{sub 3}O{sub 12} nanopowders. Thermogravimetric analysis proved that a calcination temperature of 900 C is sufficient for the preparation of single-phase bismuth titanate. X-ray diffraction and Fourier transform infrared spectroscopy are used to examine the influence of calcination temperature on the structural growth of the Bi{sub 4}Ti{sub 3}O{sub 12} nanopowder. The average crystallite size estimated by using the Scherrer method and the Williamson-Hall method was found to increase with calcination temperature. Photoluminescence behavior as a function of calcination temperature was observed at two different excitation wavelengths of 300 nm and 420 nm. The morphology of the particles analyzed using images obtained from field emission scanning electron microscopy displayed irregular, random sized, and spherical-shaped structures. The stoichiometry and purity of the nanopowder are confirmed by energy-dispersive spectroscopy. The broadband dielectric results established the highest dielectric constant (ε{sub r} = 450) for a frequency of 100 Hz achieved with a potential capacitance of 138 pF m{sup -2}. This establishes Bi{sub 4}Ti{sub 3}O{sub 12} as a promising dielectric material for achieving high energy density capacitors for the next-generation passive devices.

Polydopamine Particle-Filled Shape-Memory Polyurethane Composites with Fast Near-Infrared Light Responsibility.

Science.gov (United States)

Yang, Li; Tong, Rui; Wang, Zhanhua; Xia, Hesheng

2018-03-25

A new kind of fast near-infrared (NIR) light-responsive shape-memory polymer composites was prepared by introducing polydopamine particles (PDAPs) into commercial shape-memory polyurethane (SMPU). The toughness and strength of the polydopamine-particle-filled polyurethane composites (SMPU-PDAPs) were significantly enhanced with the addition of PDAPs due to the strong interface interaction between PDAPs and polyurethane segments. Owing to the outstanding photothermal effect of PDAPs, the composites exhibit a rapid light-responsive shape-memory process in 60 s with a PDAPs content of 0.01 wt%. Due to the excellent dispersion and convenient preparation method, PDAPs have great potential to be used as high-efficiency and environmentally friendly fillers to obtain novel photoactive functional polymer composites. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Efficiency enhancement of semitransparent organic solar cells by using printed dielectric mirrors (Presentation Recording)

Science.gov (United States)

Bronnbauer, Carina; Forberich, Karen K.; Guo, Fei; Gasparini, Nicola; Brabec, Christoph J.

2015-09-01

Building integrated thin film solar cells are a strategy for future eco-friendly power generation. Such solar cells have to be semi-transparent, long-term stable and show the potential to be fabricated by a low-cost production process. Organic photovoltaics are a potential candidate because an absorber material with its main absorption in the infrared spectral region where the human eye is not sensitive can be chosen. We can increase the number of absorbed photons, at the same time, keep the transparency almost constant by using a dielectric, wavelength-selective mirror. The mirror reflects only in the absorption regime of the active layer material and shows high transparencies in the spectral region around 550 nm where the human eye is most sensitive. We doctor bladed a fully solution processed dielectric mirror at low temperatures below 80 °C. Both inks, which are printed alternatingly are based on nanoparticles and have a refractive index of 1.29 or 1.98, respectively, at 500 nm. The position and the intensity of the main reflection peak can be easily shifted and thus adjusted to the solar cell absorption spectrum. Eventually, the dielectric mirror was combined with different organic solar cells. For instance, the current increases by 20.6 % while the transparency decreases by 23.7 % for the low band gap absorber DPP and silver nanowires as top electrode. Moreover we proved via experiment and optical simulations, that a variation of the active layer thickness and the position of the main reflection peak affect the transparency and the increase in current.

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.

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.

Superiority of terahertz over infrared transmission through bandages and burn wound ointments

International Nuclear Information System (INIS)

Suen, Jonathan Y.; Padilla, Willie J.

2016-01-01

Terahertz electromagnetic waves have long been proposed to be ideal for spectroscopy and imaging through non-polar dielectric materials that contain no water. Terahertz radiation may thus be useful for monitoring burn and wound injury recovery, as common care treatments involve application of both a clinical dressing and topical ointment. Here, we investigate the optical properties of typical care treatments in the millimeter wave (150–300 GHz), terahertz (0.3–3 THz), and infrared (14.5–0.67 μm) ranges of the electromagnetic spectrum. We find that THz radiation realizes low absorption coefficients and high levels of transmission compared to infrared wavelengths, which were strongly attenuated. Terahertz imaging can enable safe, non-ionizing, noninvasive monitoring of the healing process directly through clinical dressings and recovery ointments, minimizing the frequency of dressing changes and thus increasing the rate of the healing process.

Superiority of terahertz over infrared transmission through bandages and burn wound ointments

Energy Technology Data Exchange (ETDEWEB)

Suen, Jonathan Y., E-mail: j.suen@duke.edu; Padilla, Willie J. [Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708 (United States)

2016-06-06

Terahertz electromagnetic waves have long been proposed to be ideal for spectroscopy and imaging through non-polar dielectric materials that contain no water. Terahertz radiation may thus be useful for monitoring burn and wound injury recovery, as common care treatments involve application of both a clinical dressing and topical ointment. Here, we investigate the optical properties of typical care treatments in the millimeter wave (150–300 GHz), terahertz (0.3–3 THz), and infrared (14.5–0.67 μm) ranges of the electromagnetic spectrum. We find that THz radiation realizes low absorption coefficients and high levels of transmission compared to infrared wavelengths, which were strongly attenuated. Terahertz imaging can enable safe, non-ionizing, noninvasive monitoring of the healing process directly through clinical dressings and recovery ointments, minimizing the frequency of dressing changes and thus increasing the rate of the healing process.

Eeonomer 200F®: A High-Performance Nanofiller for Polymer Reinforcement—Investigation of the Structure, Morphology and Dielectric Properties of Polyvinyl Alcohol/Eeonomer-200F® Nanocomposites for Embedded Capacitor Applications

Science.gov (United States)

Deshmukh, Kalim; Ahamed, M. Basheer; Deshmukh, Rajendra R.; Sadasivuni, Kishor Kumar; Ponnamma, Deepalekshmi; Pasha, S. K. Khadheer; AlMaadeed, Mariam Al-Ali; Polu, Anji Reddy; Chidambaram, K.

2017-04-01

In the present study, Eeonomer 200F® was used as a high-performance nanofiller to prepare polyvinyl alcohol (PVA)-based nanocomposite films using a simple and eco-friendly solution casting technique. The prepared PVA/Eeonomer nanocomposite films were further investigated using various techniques including Fourier transform infrared spectroscopy, x-ray diffraction, thermogravimetric analysis, polarized optical microscopy, scanning electron microscopy and mechanical testing. The dielectric behavior of the nanocomposites was examined over a broad frequency range from 50 Hz to 20 MHz and temperatures ranging from 40°C to 150°C. A notable improvement in the thermal stability of the PVA was observed with the incorporation of Eeonomer. The nanocomposites also demonstrated improved mechanical properties due to the fine dispersion of the Eeonomer, and good compatibility and strong interaction between the Eeonomer and the PVA matrix. A significant improvement was observed in the dielectric properties of the PVA upon the addition of Eeonomer. The nanocomposites containing 5 wt.% Eeonomer exhibited a dielectric constant of about 222.65 (50 Hz, 150°C), which was 18 times that of the dielectric constant (12.33) of neat PVA film under the same experimental conditions. These results thus indicate that PVA/Eeonomer nanocomposites can be used as a flexible high-k dielectric material for embedded capacitor applications.

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.

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

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.

Design of Rose Bengal/FTO optical thin film system as a novel nonlinear media for infrared blocking windows

Directory of Open Access Journals (Sweden)

S.M. El-Bashir

Full Text Available Rose Bengal (RB is a new organic semiconductor with the highly stable layer, was deposited on highly cleaned conductive glass substrate known as (FTO glass with different thickness in the range from 80 to 292 nm. XRD showed an entirely amorphous structure of the studied film thicknesses. The observed peaks are the indexed peaks for FTO layer. Spectrophotometric data as transmittance, reflectance, and absorbance were used for the analysis the optical constant of RB/FTO optical thin film system. Refractive index was calculated using Fresnel’s equation with the aid of reflectance and absorption index. The dielectric constant, dielectric loss and dissipation factor were discussed and analyzed according to the applied optical theories. Nonlinear parameters such as third order nonlinear optical susceptibility and the nonlinear refractive index were calculated based on the linear refractive index of the applications of this material in nonlinear media. The results showed that Rose Bengal is a proving material for wide scale optoelectronic applications such as infrared blocking windows. Keywords: Rose Bengal, Dielectric parameters, Linear/nonlinear optics, Dye/FTO, IR blocking windows

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.

A study on the optical, structural, electrical conductivity and dielectric properties of a lithium bismuth germanium tungsten glasses

Energy Technology Data Exchange (ETDEWEB)

Salem, Shaaban M., E-mail: shaabansalem@gmail.com [Department of Physics, Faculty of Science, Al Azhar University, Nasr City 11884, Cairo (Egypt); Abdel-Khalek, E.K. [Department of Physics, Faculty of Science, Al Azhar University, Nasr City 11884, Cairo (Egypt); Department of Physics, Faculty of Science, Jazan University (Saudi Arabia); Mohamed, E.A. [Department of Physics, Faculty of Science (Girl' s Branch), Al Azhar University, Nasr City, Cairo (Egypt); Department of Physics, Faculty of Science, Jazan University (Saudi Arabia); Farouk, M. [Department of Physics, Faculty of Science, Al Azhar University, Nasr City 11884, Cairo (Egypt); Department of Physics, Faculty of Science, Jazan University (Saudi Arabia)

2012-02-05

Highlights: Black-Right-Pointing-Pointer I report, for the first time, the effect of WO{sub 3} on Bi{sub 2}O{sub 3}, Li{sub 2}O, GeO{sub 2} and WO{sub 3} glasses through structural, optical, conductivity and dielectric studies. Black-Right-Pointing-Pointer Optical band gap E{sub op} for all types of electronic transitions, Urbach energy (E{sub r}), and refractive index determined. Black-Right-Pointing-Pointer The WO{sub 3} promotes as bitter constituent the reduction of W{sup 6+} to W{sup 5+} giving the bluish color. Black-Right-Pointing-Pointer Infrared spectra reveal characteristic GeO{sub 4}, GeO{sub 6}, Bi{sub 2}O{sub 3}, BiO{sub 6}, WO{sub 4} and WO{sub 6} units. Black-Right-Pointing-Pointer Based on ac and dc conductivity the conductivity increased and activation energies decreased with increase of WO{sub 3} content at all frequencies. - Abstract: Glasses in the system (65 - x)Bi{sub 2}O{sub 3}-15Li{sub 2}O-20GeO{sub 2}-xWO{sub 3} (where x = 2, 5 and 10 mol%) were prepared by normal melt quenching method. The change in density and molar volume in these glasses indicates the effect of WO{sub 3} on the glass structure. Fourier transform infrared (FT-IR) spectra show that these glasses are made up of GeO{sub 4}, GeO{sub 6}, BiO{sub 6}, BiO{sub 3}, WO{sub 4} and WO{sub 6} basic structural units. The structural units of BiO{sub 6}, GeO{sub 6} and WO{sub 6} increase with the increasing of WO{sub 3} content. The optical constants of these glasses are determined over a spectral range, providing the complex dielectric constant to be calculated. Higher values for the refractive index and dispersion are recorded due to the high polarizability of bismuth and tungsten ions. The values of the optical band gap E{sub g} for all types of electronic transitions and refractive index have been determined and discussed. The dc conductivity measured in the temperature range 423-623 K obeys Arrhenius law. The dielectric constant ({epsilon} Prime ), dielectric loss (tan {delta}) and

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)