Negative Dielectric Constant Material Based on Ion Conducting Materials

NASA Technical Reports Server (NTRS)

Gordon, Keith L. (Inventor); Kang, Jin Ho (Inventor); Park, Cheol (Inventor); Lillehei, Peter T. (Inventor); Harrison, Joycelyn S. (Inventor)

2017-01-01

Metamaterials or artificial negative index materials (NIMs) have generated great attention due to their unique and exotic electromagnetic properties. One exemplary negative dielectric constant material, which is an essential key for creating the NIMs, was developed by doping ions into a polymer, a protonated poly (benzimidazole) (PBI). The doped PBI showed a negative dielectric constant at megahertz (MHz) frequencies due to its reduced plasma frequency and an induction effect. The magnitude of the negative dielectric constant and the resonance frequency were tunable by doping concentration. The highly doped PBI showed larger absolute magnitude of negative dielectric constant at just above its resonance frequency than the less doped PBI.

Negative Dielectric Constant Material Based on Ion Conducting Materials

NASA Technical Reports Server (NTRS)

Gordon, Keith L. (Inventor); Kang, Jin Ho (Inventor); Harrison, Joycelyn S. (Inventor); Park, Cheol (Inventor); Lillehei, Peter T. (Inventor)

2014-01-01

Metamaterials or artificial negative index materials (NIMs) have generated great attention due to their unique and exotic electromagnetic properties. One exemplary negative dielectric constant material, which is an essential key for creating the NIMs, was developed by doping ions into a polymer, a protonated poly(benzimidazole) (PBI). The doped PBI showed a negative dielectric constant at megahertz (MHz) frequencies due to its reduced plasma frequency and an induction effect. The magnitude of the negative dielectric constant and the resonance frequency were tunable by doping concentration. The highly doped PBI showed larger absolute magnitude of negative dielectric constant at just above its resonance frequency than the less doped PBI.

Submillimeter and Far-Infrared Dielectric Properties of Thin Films

NASA Technical Reports Server (NTRS)

Cataldo, Giuseppe; Wollack, Edward J.

2016-01-01

The complex dielectric function enables the study of a material's refractive and absorptive properties and provides information on a material's potential for practical application. Commonly employed line shape profile functions from the literature are briefly surveyed and their suitability for representation of dielectric material properties are discussed. An analysis approach to derive a material's complex dielectric function from observed transmittance spectra in the far-infrared and submillimeter regimes is presented. The underlying model employed satisfies the requirements set by the Kramers-Kronig relations. The dielectric function parameters derived from this approach typically reproduce the observed transmittance spectra with an accuracy of less than 4%.

Wave attenuation and mode dispersion in a waveguide coated with lossy dielectric material

NASA Technical Reports Server (NTRS)

Lee, C. S.; Chuang, S. L.; Lee, S. W.; Lo, Y. T.

1984-01-01

The modal attenuation constants in a cylindrical waveguide coated with a lossy dielectric material are studied as functions of frequency, dielectric constant, and thickness of the dielectric layer. A dielectric material best suited for a large attenuation is suggested. Using Kirchhoff's approximation, the field attenuation in a coated waveguide which is illuminated by a normally incident plane wave is also studied. For a circular guide which has a diameter of two wavelengths and is coated with a thin lossy dielectric layer (omega sub r = 9.1 - j2.3, thickness = 3% of the radius), a 3 dB attenuation is achieved within 16 diameters.

High-throughput screening of inorganic compounds for the discovery of novel dielectric and optical materials

DOE PAGES

Petousis, Ioannis; Mrdjenovich, David; Ballouz, Eric; ...

2017-01-31

Dielectrics are an important class of materials that are ubiquitous in modern electronic applications. Even though their properties are important for the performance of devices, the number of compounds with known dielectric constant is on the order of a few hundred. Here, we use Density Functional Perturbation Theory as a way to screen for the dielectric constant and refractive index of materials in a fast and computationally efficient way. Our results constitute the largest dielectric tensors database to date, containing 1,056 compounds. Details regarding the computational methodology and technical validation are presented along with the format of our publicly availablemore » data. In addition, we integrate our dataset with the Materials Project allowing users easy access to material properties. Finally, we explain how our dataset and calculation methodology can be used in the search for novel dielectric compounds.« less

High-throughput screening of inorganic compounds for the discovery of novel dielectric and optical materials

PubMed Central

Petousis, Ioannis; Mrdjenovich, David; Ballouz, Eric; Liu, Miao; Winston, Donald; Chen, Wei; Graf, Tanja; Schladt, Thomas D.; Persson, Kristin A.; Prinz, Fritz B.

2017-01-01

Dielectrics are an important class of materials that are ubiquitous in modern electronic applications. Even though their properties are important for the performance of devices, the number of compounds with known dielectric constant is on the order of a few hundred. Here, we use Density Functional Perturbation Theory as a way to screen for the dielectric constant and refractive index of materials in a fast and computationally efficient way. Our results constitute the largest dielectric tensors database to date, containing 1,056 compounds. Details regarding the computational methodology and technical validation are presented along with the format of our publicly available data. In addition, we integrate our dataset with the Materials Project allowing users easy access to material properties. Finally, we explain how our dataset and calculation methodology can be used in the search for novel dielectric compounds. PMID:28140408

High-throughput screening of inorganic compounds for the discovery of novel dielectric and optical materials.

PubMed

Petousis, Ioannis; Mrdjenovich, David; Ballouz, Eric; Liu, Miao; Winston, Donald; Chen, Wei; Graf, Tanja; Schladt, Thomas D; Persson, Kristin A; Prinz, Fritz B

2017-01-31

Dielectrics are an important class of materials that are ubiquitous in modern electronic applications. Even though their properties are important for the performance of devices, the number of compounds with known dielectric constant is on the order of a few hundred. Here, we use Density Functional Perturbation Theory as a way to screen for the dielectric constant and refractive index of materials in a fast and computationally efficient way. Our results constitute the largest dielectric tensors database to date, containing 1,056 compounds. Details regarding the computational methodology and technical validation are presented along with the format of our publicly available data. In addition, we integrate our dataset with the Materials Project allowing users easy access to material properties. Finally, we explain how our dataset and calculation methodology can be used in the search for novel dielectric compounds.

Dyakonov surface waves at the interface between hexagonal-boron-nitride and isotropic material

NASA Astrophysics Data System (ADS)

Zhu, B.; Ren, G.; Gao, Y.; Wang, Q.; Wan, C.; Wang, J.; Jian, S.

2016-12-01

In this paper we analyze the propagation of Dyakonov surface waves (DSWs) at the interface between hexagonal-boron-nitride (h-BN) and isotropic dielectric material. Various properties of DSWs supported at the dielectric-elliptic and dielectric-hyperbolic types of interfaces have been theoretically investigated, including the real effective index, propagation length, the angular existence domain (AED) and the composition ratio of evanescent field components in an h-BN crystal and isotropic dielectric material, respectively. The analysis in this paper reveals that h-BN could be a promising anisotropic material to observe the propagation of DSWs and may have potential diverse applications, such as high sensitivity stress sensing or optical sensing of analytes infiltrating dielectric materials.

Dielectric property measurements in the Electromagnetic Properties Measurement Laboratory

NASA Technical Reports Server (NTRS)

Cravey, Robin L.; Tiemsin, Pacita I.; Bussell, Kerri; Dudley, Kenneth L.

1995-01-01

The capability to measure the dielectric properties of various materials has been developed in the Electromagnetic Properties Measurement Laboratory (EPML) of the Electromagnetics Research Branch (ERB). Two measurement techniques which have been implemented in the EPML to characterize materials are the dielectric probe and waveguide techniques. Several materials, including some for which the dielectric properties are well known, have been measured in an attempt to establish the capabilities of the EPML in determining dielectric properties. Brief descriptions of the two techniques are presented in this report, along with representative results obtained during these measurements.

High dielectric hyperbranched polyaniline materials.

PubMed

Yan, X Z; Goodson, T

2006-08-03

New organic materials for the purpose of high speed capacitor applications are discussed. The effect of the microcrystalline size dependence of different polyaniline polymeric systems on the dielectric constant is investigated. Two different methods are described for the preparation of the polyaniline dielectric materials. By sonication polymerization, the prepared polyaniline with a suggested hyperbranched structure showed much larger microcrystalline domains in comparison to the conventional linear polyaniline. Investigations of the dielectric constant and capacitance at a relatively high frequency (>100 kHz) suggested that the system with the larger microcrystalline domains (hyperbranched) gives rise to a larger dielectric constant. The mechanism of the increased dielectric response at higher frequencies is investigated by EPR spectroscopy, and these results suggest that delocalized polarons may provide a way to enhance the dielectric response at high frequency.

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

PubMed

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.

Negative Refraction in a Uniaxial Absorbent Dielectric Material

ERIC Educational Resources Information Center

Jen, Yi-Jun; Lakhtakia, Akhlesh; Yu, Ching-Wei; Lin, Chin-Te

2009-01-01

Refraction of light from an isotropic dielectric medium to an anisotropic dielectric material is a complicated phenomenon that can have several different characteristics not usually discussed in electromagnetics textbooks for undergraduate students. With a simple problem wherein the refracting material is uniaxial with its optic axis normal to the…

Computational screening of organic polymer dielectrics for novel accelerator technologies

DOE PAGES

Pilania, Ghanshyam; Weis, Eric; Walker, Ethan M.; ...

2018-06-18

The use of infrared lasers to power accelerating dielectric structures is a developing area of research. Within this technology, the choice of the dielectric material forming the accelerating structures, such as the photonic band gap (PBG) structures, is dictated by a range of interrelated factors including their dielectric and optical properties, amenability to photo-polymerization, thermochemical stability and other target performance metrics of the particle accelerator. In this direction, electronic structure theory aided computational screening and design of dielectric materials can play a key role in identifying potential candidate materials with the targeted functionalities to guide experimental synthetic efforts. In anmore » attempt to systematically understand the role of chemistry in controlling the electronic structure and dielectric properties of organic polymeric materials, here we employ empirical screening and density functional theory (DFT) computations, as a part of our multi-step hierarchal screening strategy. Our DFT based analysis focused on the bandgap, dielectric permittivity, and frequency-dependent dielectric losses due to lattice absorption as key properties to down-select promising polymer motifs. In addition to the specific application of dielectric laser acceleration, the general methodology presented here is deemed to be valuable in the design of new insulators with an attractive combination of dielectric properties.« less

Dielectric spectroscopy in agrophysics

NASA Astrophysics Data System (ADS)

Skierucha, W.; Wilczek, A.; Szypłowska, A.

2012-04-01

The paper presents scientific foundation and some examples of agrophysical applications of dielectric spectroscopy techniques. The aim of agrophysics is to apply physical methods and techniques for studies of materials and processes which occur in agriculture. Dielectric spectroscopy, which describes the dielectric properties of a sample as a function of frequency, may be successfully used for examinations of properties of various materials. Possible test materials may include agrophysical objects such as soil, fruit, vegetables, intermediate and final products of the food industry, grain, oils, etc. Dielectric spectroscopy techniques enable non-destructive and non-invasive measurements of the agricultural materials, therefore providing tools for rapid evaluation of their water content and quality. There is a limited number of research in the field of dielectric spectroscopy of agricultural objects, which is caused by the relatively high cost of the respective measurement equipment. With the fast development of modern technology, especially in high frequency applications, dielectric spectroscopy has great potential of expansion in agrophysics, both in cognitive and utilitarian aspects.

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

PubMed Central

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

2016-01-01

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

Influence of Surrounding Dielectrics on the Data Retention Time of Doped Sb2Te Phase Change Material

NASA Astrophysics Data System (ADS)

Jedema, Friso; in `t Zandt, Micha; Wolters, Rob; Gravesteijn, Dirk

2011-02-01

The crystallization properties of as-deposited and laser written amorphous marks of doped Sb2Te phase change material are found to be only dependent on the top dielectric layer. A ZnS:SiO2 top dielectric layer yields a higher crystallization temperature and a larger crystal growth activation energy as compared to a SiO2 top dielectric layer, leading to superior data retention times at ambient temperatures. The observed correlation between the larger crystallization temperatures and larger crystal growth activation energies indicates that the viscosity of the phase change material in the amorphous state is dependent on the interfacial energy between the phase change material and the top dielectric layer.

Dielectric-Particle Injector For Processing Of Materials

NASA Technical Reports Server (NTRS)

Leung, Philip L.; Gabriel, Stephen B.

1992-01-01

Device generates electrically charged particles of solid, or droplets of liquid, fabricated from dielectric material and projects them electrostatically, possibly injecting them into electrostatic-levitation chamber for containerless processing. Dielectric-particle or -droplet injector charges dielectric particles or droplets on zinc plate with photo-electrons generated by ultraviolet illumination, then ejects charged particles or droplets electrostatically from plate.

Viking landing sites, remote-sensing observations, and physical properties of Martian surface materials

USGS Publications Warehouse

Moore, H.J.; Jakosky, B.M.

1989-01-01

Important problems that confront future scientific exploration of Mars include the physical properties of Martian surface materials and the geologic processes that formed the materials. The design of landing spacecraft, roving vehicles, and sampling devices and the selection of landing sites, vehicle traverses, and sample sites will be, in part, guided by the physical properties of the materials. Four materials occur in the sample fields of the Viking landers: (1) drift, (2) crusty to cloddy, (3) blocky, and (4) rock. The first three are soillike. Drift materials is weak, loose, and porous. We estimate that it has a dielectric constant near 2.4 and a thermal inertia near 1 ?? 10-3 to 3 ?? 10-3 (cal cm-2 sec 1 2 K-1) because of its low bulk density, fine grain size, and small cohesion. Crusty to cloddy material is expected to have a dielectric constant near 2.8 and a thermal inertia near 4 ?? 10-3 to 7 ?? 10-3 because of its moderate bulk density and cementation of grains. Blocky material should have a dielectric constant near 3.3 and a thermal inertia near 7 ?? 10-3 to 9 ?? 10-3 because of its moderate bulk density and cementation. Common basaltic rocks have dielectric constans near 8 and thermal inertias near 30 ?? 10-3 to 60 ?? 10-3. Comparisons of estimated dielectric constants and thermal inertias of the materials at the landing sites with those obtained remotely by Earth-based radars and Viking Orbiter thermal sensors suggest that the materials at the landing sites are good analogs for materials elsewhere on Mars. Correlation of remotely estimated dielectric constant and thermal inertias indicates two modal values for paired values of dielectric constants and thermal inertias near (A) 2 and 2 ?? 10-3 and (B) 3 and 6 ?? 10-3, respectively. These two modes are comparable to the dielectric constants and thermal inertias for drift and crusty to cloddy material, respectively. Dielectric constants and thermal inertias for blocky material are larger but conistent with values in the northern plains. Our interprertations are compatible with an aeolian origin for drift and similar materials elsewhere on Mars. The postulate that moderate dielectric constants and thermal inertias larger than 3 or 4 ?? 10-3 are produced by cementation of soillike materials is partly consistent with the data. The average dielectric constant and thermal inertia and their correlation with one another suggest that most of the surface of Mars should present few difficulties to future surface exploration, but some surfaces may present difficulties for spacecraft that are not suitably designed. ?? 1989.

Exploratory studies of new avenues to achieve high electromechanical response and high dielectric constant in polymeric materials

NASA Astrophysics Data System (ADS)

Huang, Cheng

High performance soft electronic materials are key elements in advanced electronic devices for broad range applications including capacitors, actuators, artificial muscles and organs, smart materials and structures, microelectromechanical (MEMS) and microfluidic devices, acoustic devices and sensors. This thesis exploits new approaches to improve the electromechanical response and dielectric response of these materials. By making use of novel material phenomena such as large anisotropy in dipolar response in liquid crystals (LCs) and all-organic composites in which high dielectric constant organic solids and conductive polymers are either physically blended into or chemically grafted to a polymer matrix, we demonstrate that high dielectric constant and high electromechanical conversion efficiency comparable to that in ceramic materials can be achieved. Nano-composite approach can also be utilized to improve the performance of the electronic electroactive polymers (EAPs) and composites, for example, exchange coupling between the fillers and matrix with very large dielectric contrast can lead to significantly enhance the dielectric response as well as electromechanical response when the heterogeneity size of the composite is comparable to the exchange length. In addition to the dielectric composites, in which high dielectric constant fillers raise the dielectric constant of composites, conductive percolation can also lead to high dielectric constant in polymeric materials. An all-polymer percolative composite is introduced which exhibits very high dielectric constant (>7,000). The flexible all-polymer composites with a high dielectric constant make it possible to induce a high electromechanical response under a much reduced electric field in the field effect electroactive polymer (EAP) actuators (a strain of 2.65% with an elastic energy density of 0.18 J/cm3 can be achieved under a field of 16 V/mum). Agglomeration of the particles can also be effectively prevented by in situ preparation. High dielectric constant copper phthalocyanine oligomer and conductive polyaniline oligomer were successfully bonded to polyurethane backbone to form fully functionalized nano-phase polymers. Improvement of dispersibility of oligomers in polymer matrix makes the system self-organize the nanocomposites possessing oligomer nanophase (below 30nm) within the fully functionalized polymers. The resulting nanophase polymers significantly enhance the interface effect, which through the exchange coupling raises the dielectric response markedly above that expected from simple mixing rules for dielectric composites. Consequently, these nano-phase polymers offer a high dielectric constant (a dielectric constant near 1,000 at 20 Hz), improve the breakdown field and mechanical properties, and exhibit high electromechanical response. A longitudinal strain of more than -14% can be induced under a much reduced field, 23 V/mum, with an elastic energy density of higher than 1 J/cm3. The elastic modulus is as high as 100MPa, and a transverse strain is 7% under the same field. (Abstract shortened by UMI.)

Dielectric Characterization of a Nonlinear Optical Material

PubMed Central

Lunkenheimer, P.; Krohns, S.; Gemander, F.; Schmahl, W. W.; Loidl, A.

2014-01-01

Batisite was reported to be a nonlinear optical material showing second harmonic generation. Using dielectric spectroscopy and polarization measurements, we provide a thorough investigation of the dielectric and charge-transport properties of this material. Batisite shows the typical characteristics of a linear lossy dielectric. No evidence for ferro- or antiferroelectric polarization is found. As the second-harmonic generation observed in batisite points to a non-centrosymmetric structure, this material is piezoelectric, but most likely not ferroelectric. In addition, we found evidence for hopping charge transport of localized charge carriers and a relaxational process at low temperatures. PMID:25109553

Metal clusters and nanoparticles in dielectric matrices: Formation and optical properties

NASA Astrophysics Data System (ADS)

Gladskikh, I. A.; Vartanyan, T. A.

2016-12-01

The optical properties of thin dielectric films with metal inclusions and their dependence on thermal and laser annealing are studied experimentally. Metal clusters (Ag, Au, and Cu) in dielectric materials (Al2O3 and SiO2) are obtained by simultaneous vacuum deposition of metal and dielectric on the surface of a corresponding dielectric substrate (sapphire and quartz). It is shown that, depending on the deposited dielectric material, on the weight ratio of deposited metal and dielectric, and on the subsequent thermal treatment, one can obtain different metal structures, from clusters with a small number of atoms to complex dendritic plasmonic structures.

Optimization of dielectric matrix for ZnO nanowire based nanogenerators

NASA Astrophysics Data System (ADS)

Kannan, Santhosh; Parmar, Mitesh; Tao, Ran; Ardila, Gustavo; Mouis, Mireille

2016-11-01

This paper reports the role of selection of suitable dielectric layer in nanogenerator (NG) structure and its influence on the output performance. The basic NG structure is a composite material integrating hydrothermally grown vertical piezoelectric zinc oxide (ZnO) nanowires (NWs) into a dielectric matrix. To accomplish this study, three materials - poly methyl methacrylate (PMMA), silicon nitride (Si3N4) and aluminium oxide (Al2O3) are selected, processed and used as matrix dielectric in NGs. Scanning electron microscopy (SEM) analysis shows the well-aligned NWs with a diameter of 200±50 nm and length of 3.5±0.3 μm. This was followed by dielectric material deposition as a matrix material. After fabricating NG devices, the output generated voltage under manual and automatic bending were recorded, observed and analyzed for the selection of the best dielectric material to obtain an optimum output. The maximum peak-to-peak open-circuit voltage output for PMMA, Si3N4 and Al2O3 under manual bending was recorded as approximately 880 mV, 1.2 V and 2.1 V respectively. These preliminary results confirm the predicted effect of using more rigid dielectrics as matrix material for the NGs. The generated voltage is increased by about 70% using Si3N4 or Al2O3, instead of a less rigid material as PMMA.

Organic solar cells based on high dielectric constant materials: An approach to increase efficiency

NASA Astrophysics Data System (ADS)

Hamam, Khalil Jumah Tawfiq

The efficiency of organic solar cells still lags behind inorganic solar cells due to their low dielectric constant which results in a weakly screened columbic attraction between the photogenerated electron-hole system, therefore the probability of charge separating is low. Having an organic material with a high dielectric constant could be the solution to get separated charges or at least weakly bounded electron-hole pairs. Therefore, high dielectric constant materials have been investigated and studied by measuring modified metal-phthalocyanine (MePc) and polyaniline in pellets and thin films. The dielectric constant was investigated as a function of temperature and frequency in the range of 20Hz to1MHz. For MePc we found that the high dielectric constant was an extrinsic property due to water absorption and the formation of hydronuim ion allowed by the ionization of the functional groups such as sulphonated and carboxylic groups. The dielectric constant was high at low frequencies and decreasing as the frequency increase. Investigated materials were applied in fabricated bilayer heterojunction organic solar cells. The application of these materials in an organic solar cells show a significant stability under room conditions rather than improvement in their efficiency.

Fluorinated graphene as high performance dielectric materials and the applications for graphene nanoelectronics.

PubMed

Ho, Kuan-I; Huang, Chi-Hsien; Liao, Jia-Hong; Zhang, Wenjing; Li, Lain-Jong; Lai, Chao-Sung; Su, Ching-Yuan

2014-07-31

There is broad interest in surface functionalization of 2D materials and its related applications. In this work, we present a novel graphene layer transistor fabricated by introducing fluorinated graphene (fluorographene), one of the thinnest 2D insulator, as the gate dielectric material. For the first time, the dielectric properties of fluorographene, including its dielectric constant, frequency dispersion, breakdown electric field and thermal stability, were comprehensively investigated. We found that fluorographene with extremely thin thickness (5 nm) can sustain high resistance at temperature up to 400 °C. The measured breakdown electric field is higher than 10 MV cm(-1), which is the heightest value for dielectric materials in this thickness. Moreover, a proof-of-concept methodology, one-step fluorination of 10-layered graphene, is readily to obtain the fluorographene/graphene heterostructures, where the top-gated transistor based on this structure exhibits an average carrier mobility above 760 cm(2)/Vs, higher than that obtained when SiO₂ and GO were used as gate dielectric materials. The demonstrated fluorographene shows excellent dielectric properties with fast and scalable processing, providing a universal applications for the integration of versatile nano-electronic devices.

Fluorinated Graphene as High Performance Dielectric Materials and the Applications for Graphene Nanoelectronics

PubMed Central

Ho, Kuan-I; Huang, Chi-Hsien; Liao, Jia-Hong; Zhang, Wenjing; Li, Lain-Jong; Lai, Chao-Sung; Su, Ching-Yuan

2014-01-01

There is broad interest in surface functionalization of 2D materials and its related applications. In this work, we present a novel graphene layer transistor fabricated by introducing fluorinated graphene (fluorographene), one of the thinnest 2D insulator, as the gate dielectric material. For the first time, the dielectric properties of fluorographene, including its dielectric constant, frequency dispersion, breakdown electric field and thermal stability, were comprehensively investigated. We found that fluorographene with extremely thin thickness (5 nm) can sustain high resistance at temperature up to 400°C. The measured breakdown electric field is higher than 10 MV cm−1, which is the heightest value for dielectric materials in this thickness. Moreover, a proof-of-concept methodology, one-step fluorination of 10-layered graphene, is readily to obtain the fluorographene/graphene heterostructures, where the top-gated transistor based on this structure exhibits an average carrier mobility above 760 cm2/Vs, higher than that obtained when SiO2 and GO were used as gate dielectric materials. The demonstrated fluorographene shows excellent dielectric properties with fast and scalable processing, providing a universal applications for the integration of versatile nano-electronic devices. PMID:25081226

Voltage sensor and dielectric material

DOEpatents

Yakymyshyn, Christopher Paul; Yakymyshyn, Pamela Jane; Brubaker, Michael Allen

2006-10-17

A voltage sensor is described that consists of an arrangement of impedance elements. The sensor is optimized to provide an output ratio that is substantially immune to changes in voltage, temperature variations or aging. Also disclosed is a material with a large and stable dielectric constant. The dielectric constant can be tailored to vary with position or direction in the material.

Resonant dielectric metamaterials

DOEpatents

Loui, Hung; Carroll, James; Clem, Paul G; Sinclair, Michael B

2014-12-02

A resonant dielectric metamaterial comprises a first and a second set of dielectric scattering particles (e.g., spheres) having different permittivities arranged in a cubic array. The array can be an ordered or randomized array of particles. The resonant dielectric metamaterials are low-loss 3D isotropic materials with negative permittivity and permeability. Such isotropic double negative materials offer polarization and direction independent electromagnetic wave propagation.

High-κ gate dielectrics: Current status and materials properties considerations

NASA Astrophysics Data System (ADS)

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

2001-05-01

Many materials systems are currently under consideration as potential replacements for SiO2 as the gate dielectric material for sub-0.1 μm complementary metal-oxide-semiconductor (CMOS) technology. A systematic consideration of the required properties of gate dielectrics indicates that the key guidelines for selecting an alternative gate dielectric are (a) permittivity, band gap, and band alignment to silicon, (b) thermodynamic stability, (c) film morphology, (d) interface quality, (e) compatibility with the current or expected materials to be used in processing for CMOS devices, (f) process compatibility, and (g) reliability. Many dielectrics appear favorable in some of these areas, but very few materials are promising with respect to all of these guidelines. A review of current work and literature in the area of alternate gate dielectrics is given. Based on reported results and fundamental considerations, the pseudobinary materials systems offer large flexibility and show the most promise toward successful integration into the expected processing conditions for future CMOS technologies, especially due to their tendency to form at interfaces with Si (e.g. silicates). These pseudobinary systems also thereby enable the use of other high-κ materials by serving as an interfacial high-κ layer. While work is ongoing, much research is still required, as it is clear that any material which is to replace SiO2 as the gate dielectric faces a formidable challenge. The requirements for process integration compatibility are remarkably demanding, and any serious candidates will emerge only through continued, intensive investigation.

New dielectric elastomers with improved properties for energy harvesting and actuation

NASA Astrophysics Data System (ADS)

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

2015-02-01

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

Synthesis and Characterization of High-Dielectric-Constant Nanographite-Polyurethane Composite

NASA Astrophysics Data System (ADS)

Mishra, Praveen; Bhat, Badekai Ramachandra; Bhattacharya, B.; Mehra, R. M.

2018-05-01

In the face of ever-growing demand for capacitors and energy storage devices, development of high-dielectric-constant materials is of paramount importance. Among various dielectric materials available, polymer dielectrics are preferred for their good processability. We report herein synthesis and characterization of nanographite-polyurethane composite with high dielectric constant. Nanographite showed good dispersibility in the polyurethane matrix. The thermosetting nature of polyurethane gives the composite the ability to withstand higher temperature without melting. The resultant composite was studied for its dielectric constant (ɛ) as a function of frequency. The composite exhibited logarithmic variation of ɛ from 3000 at 100 Hz to 225 at 60 kHz. The material also exhibited stable dissipation factor (tan δ) across the applied frequencies, suggesting its ability to resist current leakage.

Compton effect thermally activated depolarization dosimeter

DOEpatents

Moran, Paul R.

1978-01-01

A dosimetry technique for high-energy gamma radiation or X-radiation employs the Compton effect in conjunction with radiation-induced thermally activated depolarization phenomena. A dielectric material is disposed between two electrodes which are electrically short circuited to produce a dosimeter which is then exposed to the gamma or X radiation. The gamma or X-radiation impinging on the dosimeter interacts with the dielectric material directly or with the metal composing the electrode to produce Compton electrons which are emitted preferentially in the direction in which the radiation was traveling. A portion of these electrons becomes trapped in the dielectric material, consequently inducing a stable electrical polarization in the dielectric material. Subsequent heating of the exposed dosimeter to the point of onset of ionic conductivity with the electrodes still shorted through an ammeter causes the dielectric material to depolarize, and the depolarization signal so emitted can be measured and is proportional to the dose of radiation received by the dosimeter.

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

PubMed Central

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

2016-01-01

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 < 0.01) obtained on Bi0.95Y0.05FeO3 films epitaxially grown on SrTiO3 (001) by pulsed laser deposition. High resolution transmission electron microscopy and geometric phase analysis evidenced nanostripe domains with alternating compressive/tensile strain and slight lattice rotations. Nanoscale mixed phase/domain ensembles are commonly found in different complex materials with giant dielectric/electromechanical (ferroelectric/ relaxors) or magnetoresistance (manganites) response. Our work brings insight into the joined role of chemical pressure and epitaxial strain on the appearance of nanoscale stripe structure which creates conditions for easy reorientation and high dielectric response, and could be of more general relevance for the field of materials science where engineered materials with huge response to external stimuli are a highly priced target. PMID:27157090

Laser-driven interactions and resultant instabilities in materials with high dielectric constant

NASA Astrophysics Data System (ADS)

Rajpoot, Moolchandra; Dixit, Sanjay

2015-07-01

An analytical investigation of nonlinear interactions resulting in parametric amplification of acoustic wave is made by obtaining the dispersion relation using hydrodynamic model of inhomogeneous plasma by applying large static field at an arbitrary angle with the pump wave. The investigation shows that many early studies have neglected dependence of dielectric constant on deformation of materials but deformation of materials does infect depends on the dielectric constant of medium. Thus we have assumed to high dielectric material like BaTiO3 which resulted in substantially high growth rate of threshold electric field which opens a new dimension to study nonlinear interactions and instabilities.

Method of using sacrificial materials for fabricating internal cavities in laminated dielectric structures

DOEpatents

Peterson, Kenneth A [Albuquerque, NM

2009-02-24

A method of using sacrificial materials for fabricating internal cavities and channels in laminated dielectric structures, which can be used as dielectric substrates and package mounts for microelectronic and microfluidic devices. A sacrificial mandrel is placed in-between two or more sheets of a deformable dielectric material (e.g., unfired LTCC glass/ceramic dielectric), wherein the sacrificial mandrel is not inserted into a cutout made in any of the sheets. The stack of sheets is laminated together, which deforms the sheet or sheets around the sacrificial mandrel. After lamination, the mandrel is removed, (e.g., during LTCC burnout), thereby creating a hollow internal cavity in the monolithic ceramic structure.

Alkali resistant optical coatings for alkali lasers and methods of production thereof

DOEpatents

Soules, Thomas F; Beach, Raymond J; Mitchell, Scott C

2014-11-18

In one embodiment, a multilayer dielectric coating for use in an alkali laser includes two or more alternating layers of high and low refractive index materials, wherein an innermost layer includes a thicker, >500 nm, and dense, >97% of theoretical, layer of at least one of: alumina, zirconia, and hafnia for protecting subsequent layers of the two or more alternating layers of high and low index dielectric materials from alkali attack. In another embodiment, a method for forming an alkali resistant coating includes forming a first oxide material above a substrate and forming a second oxide material above the first oxide material to form a multilayer dielectric coating, wherein the second oxide material is on a side of the multilayer dielectric coating for contacting an alkali.

7 CFR 1755.900 - Abbreviations and Definitions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... to §§ 1755.901 and 1755.902: (a) Abbreviations. (1) ADSSAll dielectric self-supporting; (2...) Dielectric cable means a cable which has neither metallic members nor other electrically conductive materials... means any fiber made of dielectric material that guides light. (24) Optical point discontinuities means...

7 CFR 1755.900 - Abbreviations and Definitions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... to §§ 1755.901 and 1755.902: (a) Abbreviations. (1) ADSSAll dielectric self-supporting; (2...) Dielectric cable means a cable which has neither metallic members nor other electrically conductive materials... means any fiber made of dielectric material that guides light. (24) Optical point discontinuities means...

From organized high throughput data to phenomenological theory: The example of dielectric breakdown

NASA Astrophysics Data System (ADS)

Kim, Chiho; Pilania, Ghanshyam; Ramprasad, Rampi

Understanding the behavior (and failure) of dielectric insulators experiencing extreme electric fields is critical to the operation of present and emerging electrical and electronic devices. Despite its importance, the development of a predictive theory of dielectric breakdown has remained a challenge, owing to the complex multiscale nature of this process. Here, we focus on the intrinsic dielectric breakdown field of insulators--the theoretical limit of breakdown determined purely by the chemistry of the material, i.e., the elements the material is composed of, the atomic-level structure, and the bonding. Starting from a benchmark dataset (generated from laborious first principles computations) of the intrinsic dielectric breakdown field of a variety of model insulators, simple predictive phenomenological models of dielectric breakdown are distilled using advanced statistical or machine learning schemes, revealing key correlations and analytical relationships between the breakdown field and easily accessible material properties. The models are shown to be general, and can hence guide the screening and systematic identification of high electric field tolerant materials.

Method of forming nanodielectrics

DOEpatents

Tuncer, Enis [Knoxville, TN; Polyzos, Georgios [Oak Ridge, TN

2014-01-07

A method of making a nanoparticle filled dielectric material. The method includes mixing nanoparticle precursors with a polymer material and reacting the nanoparticle mixed with the polymer material to form nanoparticles dispersed within the polymer material to form a dielectric composite.

Simultaneous Noncontact Precision Imaging of Microstructural and Thickness Variation in Dielectric Materials Using Terahertz Energy

NASA Technical Reports Server (NTRS)

Roth, Donald J (Inventor)

2011-01-01

A process for simultaneously measuring the velocity of terahertz electromagnetic radiation in a dielectric material sample without prior knowledge of the thickness of the sample and for measuring the thickness of a material sample using terahertz electromagnetic radiation in a material sample without prior knowledge of the velocity of the terahertz electromagnetic radiation in the sample is disclosed and claimed. The process evaluates, in a plurality of locations, the sample for microstructural variations and for thickness variations and maps the microstructural and thickness variations by location. A thin sheet of dielectric material may be used on top of the sample to create a dielectric mismatch. The approximate focal point of the radiation source (transceiver) is initially determined for good measurements.

A Grand Challenge for CMOS Scaling: Alternate Gate Dielectrics

NASA Astrophysics Data System (ADS)

Wallace, Robert M.

2001-03-01

Many materials systems are currently under consideration as potential replacements for SiO2 as the gate dielectric material for sub-0.13 um complementary metal oxide semiconductor (CMOS) technology. The prospect of replacing SiO2 is a formidable task because the alternate gate dielectric must provide many properties that are, at a minimum, comparable to those of SiO2 yet with a much higher permittivity. A systematic examination of the required performance of gate dielectrics suggests that the key properties to consider in the selection an alternative gate dielectric candidate are (a) permittivity, band gap and band alignment to silicon, (b) thermodynamic stability, (c) film morphology, (d) interface quality, (e) compatibility with the current or expected materials to be used in processing for CMOS devices, (f) process compatibility, and (g) reliability. Many dielectrics appear favorable in some of these areas, but very few materials are promising with respect to all of these guidelines. We will review the performance requirements for materials associated with CMOS scaling, the challenges associated with these requirements, and the state-of-the-art in current research for alternate gate dielectrics. The requirements for process integration compatibility are remarkably demanding, and any serious candidates will emerge only through continued, intensive investigation.

Evidence for power-law frequency dependence of intrinsic dielectric response in the Ca Cu3 Ti4 O12

NASA Astrophysics Data System (ADS)

Tselev, Alexander; Brooks, Charles M.; Anlage, Steven M.; Zheng, Haimei; Salamanca-Riba, Lourdes; Ramesh, R.; Subramanian, M. A.

2004-10-01

We investigated the dielectric response of CaCu3Ti4O12 (CCTO) thin films grown epitaxially on LaAlO3 (001) substrates by pulsed laser deposition. The dielectric response of the films was found to be strongly dominated by a power law in frequency, typical of materials with localized hopping charge carriers, in contrast to the Debye-like response of the bulk material. The film conductivity decreases with annealing in oxygen, and it suggests that oxygen deficit is a cause of the relatively high film conductivity. With increase of the oxygen content, the room temperature frequency response of the CCTO thin films changes from the response indicating the presence of some relatively low conducting capacitive layers to purely power law, and then toward a frequency independent response with a relative dielectric constant ɛ'˜102 . The film conductance and dielectric response decrease upon decrease of the temperature, with dielectric response being dominated by the power-law frequency dependence. Below ˜80K , the dielectric response of the films is frequency independent with ɛ' close to 102 . The results provide another piece of evidence for an extrinsic, Maxwell-Wagner type, origin of the colossal dielectric response of the bulk CCTO material, connected with electrical inhomogeneity of the bulk material.

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

USDA-ARS?s Scientific Manuscript database

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

Dielectric relaxation of high-k oxides

PubMed Central

2013-01-01

Frequency dispersion of high-k dielectrics was observed and classified into two parts: extrinsic cause and intrinsic cause. Frequency dependence of dielectric constant (dielectric relaxation), that is the intrinsic frequency dispersion, could not be characterized before considering the effects of extrinsic frequency dispersion. Several mathematical models were discussed to describe the dielectric relaxation of high-k dielectrics. For the physical mechanism, dielectric relaxation was found to be related to the degree of polarization, which depended on the structure of the high-k material. It was attributed to the enhancement of the correlations among polar nanodomain. The effect of grain size for the high-k materials' structure mainly originated from higher surface stress in smaller grain due to its higher concentration of grain boundary. PMID:24180696

Characterization and metrology implications of the 1997 NTRS

NASA Astrophysics Data System (ADS)

Class, W.; Wortman, J. J.

1998-11-01

In the Front-end (transistor forming) area of silicon CMOS device processing, several NTRS difficult challenges have been identified including; scaled and alternate gate dielectric materials, new DRAM dielectric materials, alternate gate materials, elevated contact structures, engineered channels, and large-area cost-effective silicon substrates. This paper deals with some of the characterization and metrology challenges facing the industry if it is to meet the projected needs identified in the NTRS. In the areas of gate and DRAM dielectric, scaling requires that existing material layers be thinned to maximize capacitance. For the current gate dielectric, SiO2 and its nitrided derivatives, direct tunneling will limit scaling to approximately 1.5nm for logic applications before power losses become unacceptable. Low power logic and memory applications may limit scaling to the 2.0-2.2nm range. Beyond these limits, dielectric materials having higher dielectric constant, will permit continued capacitance increases while allowing for the use of thicker dielectric layers, where tunneling may be minimized. In the near term silicon nitride is a promising SiO2 substitute material while in the longer term "high-k" materials such as tantalum pentoxide and barium strontium titanate (BST) will be required. For these latter materials, it is likely that a multilayer dielectric stack will be needed, consisting of an ultra-thin (1-2 atom layer) interfacial SiO2 layer and a high-k overlayer. Silicon wafer surface preparation control, as well as the control of composition, crystal structure, and thickness for such stacks pose significant characterization and metrology challenges. In addition to the need for new gate dielectric materials, new gate materials will be required to overcome the limitations of the current doped polysilicon gate materials. Such a change has broad ramifications on device electrical performance and manufacturing process robustness which again implies a broad range of new characterization and metrology requirements. Finally, the doped structure of the MOS transistor must scale to very small lateral and depth dimensions, and thermal budgets must be reduced to permit the retention of very abrupt highly doped drain and channel engineered structures. Eventually, the NTRS forecasts the need for an elevated contact structure. Here, there are significant challenges associated with three-dimensional dopant profiling, measurement of dopant activity in ultra-shallow device regions, as well as point defect metrology and characterization.

Non-destructive evaluation method employing dielectric electrostatic ultrasonic transducers

NASA Technical Reports Server (NTRS)

Yost, William T. (Inventor); Cantrell, Jr., John H. (Inventor)

2003-01-01

An acoustic nonlinearity parameter (.beta.) measurement method and system for Non-Destructive Evaluation (NDE) of materials and structural members novelly employs a loosely mounted dielectric electrostatic ultrasonic transducer (DEUT) to receive and convert ultrasonic energy into an electrical signal which can be analyzed to determine the .beta. of the test material. The dielectric material is ferroelectric with a high dielectric constant .di-elect cons.. A computer-controlled measurement system coupled to the DEUT contains an excitation signal generator section and a measurement and analysis section. As a result, the DEUT measures the absolute particle displacement amplitudes in test material, leading to derivation of the nonlinearity parameter (.beta.) without the costly, low field reliability methods of the prior art.

Millimeter wave and terahertz dielectric properties of biological materials

NASA Astrophysics Data System (ADS)

Khan, Usman Ansar

Broadband dielectric properties of materials can be employed to identify, detect, and characterize materials through their unique spectral signatures. In this study, millimeter wave, submillimeter wave, and terahertz dielectric properties of biological substances inclusive of liquids, solids, and powders were obtained using Dispersive Fourier Transform Spectroscopy (DFTS). Two broadband polarizing interferometers were constructed to test materials from 60 GHz to 1.2 THz. This is an extremely difficult portion of the frequency spectrum to obtain a material's dielectric properties since neither optical nor microwave-based techniques provide accurate data. The dielectric characteristics of liquids such as cyclohexane, chlorobenzene, benzene, ethanol, methanol, 1,4 dioxane, and 10% formalin were obtained using the liquid interferometer. Subsequently the solid interferometer was utilized to determine the dielectric properties of human breast tissues, which are fixed and preserved in 10% formalin. This joint collaboration with the Tufts New England Medical Center demonstrated a significant difference between the dielectric response of tumorous and non-tumorous breast tissues across the spectrum. Powders such as anthrax, flour, talc, corn starch, dry milk, and baking soda have been involved in a number of security threats and false alarms around the globe in the last decade. To be able to differentiate hoax attacks and serious security threats, the dielectric properties of common household powders were also examined using the solid interferometer to identify the powders' unique resonance peaks. A new sample preparation kit was designed to test the powder specimens. It was anticipated that millimeter wave and terahertz dielectric characterization will enable one to clearly distinguish one powder from the other; however most of the powders had relatively close dielectric responses and only Talc had a resonance signature recorded at 1.135 THz. Furthermore, due to polarization and birefringence effects, it was determined that one can not utilize the dielectric properties of powder-containing packages to differentiate hoax attacks and serious security threats.

Dielectric properties for prediction of moisture content in Vidalia onions

USDA-ARS?s Scientific Manuscript database

Microwave Sensing provides a means for nondestructively determining the amount of moisture in materials by sensing the dielectric properties of the material. In this study, dielectric properties of Vidalia onions were analyzed for moisture dependence at 13.36 GHz and 23°C for moisture content betwee...

Dielectric Loss Measurements on Raw Materials.

ERIC Educational Resources Information Center

Mwanje, J.

1980-01-01

Describes an experiment used to study dielectric properties of materials. Values of the dielectric loss tangent can be determined at low frequencies from Lissajous figures formed on an oscilloscope. Some mineral rock specimens show Debye-type relaxation peaks at frequencies in the region of 1 to 500 Hz. (Author/DS)

Poly(vinyl acetate)/clay nanocomposite materials for organic thin film transistor application.

PubMed

Park, B J; Sung, J H; Park, J H; Choi, J S; Choi, H J

2008-05-01

Nanocomposite materials of poly(vinyl acetate) (PVAc) and organoclay were fabricated, in order to be utilized as dielectric materials of the organic thin film transistor (OTFT). Spin coating condition of the nanocomposite solution was examined considering shear viscosity of the composite materials dissolved in chloroform. Intercalated structure of the PVAc/clay nanocomposites was characterized using both wide-angle X-ray diffraction and TEM. Fracture morphology of the composite film on silicon wafer was also observed by SEM. Dielectric constant (4.15) of the nanocomposite materials shows that the PVAc/clay nanocomposites are applicable for the gate dielectric materials.

Dielectric Characteristics of Microstructural Changes and Property Evolution in Engineered Materials

NASA Astrophysics Data System (ADS)

Clifford, Jallisa Janet

Heterogeneous materials are increasingly used in a wide range of applications such as aerospace, civil infrastructure, fuel cells and many others. The ability to take properties from two or more materials to create a material with properties engineered to needs is always very attractive. Hence heterogeneous materials are evolving into more complex formulations in multiple disciplines. Design of microstructure at multiple scales control the global functional properties of these materials and their structures. However, local microstructural changes do not directly cause a proportional change to the global properties (such as strength and stiffness). Instead, local changes follow an evolution process including significant interactions. Therefore, in order to understand property evolution of engineered materials, microstructural changes need to be effectively captured. Characterizing these changes and representing them by material variables will enable us to further improve our material level understanding. In this work, we will demonstrate how microstructural features of heterogeneous materials can be described quantitatively using broadband dielectric spectroscopy (BbDS). The frequency dependent dielectric properties can capture the change in material microstructure and represent these changes in terms of material variables, such as complex permittivity. These changes in terms of material properties can then be linked to a number of different conditions, such as increasing damage due to impact or fatigue. Two different broadband dielectric spectroscopy scanning modes are presented: bulk measurements and continuous scanning to measure dielectric property change as a function of position across the specimen. In this study, we will focus on ceramic materials and fiber reinforced polymer matrix composites as test bed material systems. In the first part of the thesis, we will present how different micro-structural design of porous ceramic materials can be captured 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.

Origin of colossal dielectric response in (In + Nb) co-doped TiO2 rutile ceramics: a potential electrothermal material.

PubMed

Ke, Shanming; Li, Tao; Ye, Mao; Lin, Peng; Yuan, Wenxiang; Zeng, Xierong; Chen, Lang; Huang, Haitao

2017-08-31

(In + Nb) co-doped TiO 2 (TINO) rutile is an emerging material with a colossal dielectric permittivity (CP) and a low dielectric loss over wide temperature and frequency ranges. The electrical inhomogeneous nature of TINO ceramics is demonstrated by direct local current probing with high-resolution conductive atomic force microscopy (cAFM). The CP response in TINO is found to originate from the electron-pinned defect dipole induced conductive cluster effect and the electrode effect. Two types of dielectric relaxations are simultaneously observed due to these two effects. With the given synthesis condition, we found TINO shows a highly leaky feature that impairs its application as a dielectric material. However, the fast-temperature-rising phenomenon found in this work may open a new door for TINO to be applied as a potential electrothermal material with high efficiency, oxidation-proof, high temperature stability, and energy saving.

Combinatorial Investigation of ZrO2-Based Dielectric Materials for Dynamic Random-Access Memory Capacitors

NASA Astrophysics Data System (ADS)

Kiyota, Yuji; Itaka, Kenji; Iwashita, Yuta; Adachi, Tetsuya; Chikyow, Toyohiro; Ogura, Atsushi

2011-06-01

We investigated zirconia (ZrO2)-based material libraries in search of new dielectric materials for dynamic random-access memory (DRAM) by combinatorial-pulsed laser deposition (combi-PLD). We found that the substitution of yttrium (Y) to Zr sites in the ZrO2 system suppressed the leakage current effectively. The metal-insulator-metal (MIM) capacitor property of this system showed a leakage current density of less than 5×10-7 A/cm2 and the dielectric constant was 20. Moreover, the addition of titanium (Ti) or tantalum (Ta) to this system caused the dielectric constant to increase to ˜25 within the allowed leakage level of 5×10-7 A/cm2. Therefore, Zr-Y-Ti-O and Zr-Y-Ta-O systems have good potentials for use as new materials with high dielectric constants of DRAM capacitors instead of silicon dioxides (SiO2).

An experimental setup for study direct charge battery based on Sr-90

NASA Astrophysics Data System (ADS)

Özkeçeci, S.; Koç, R.

2017-02-01

In this paper we present construction and analysis of nuclear micro battery driven by Strontium 90 (Sr-90). Our design based on charge deposition on the plates of a capacitor and polarization of dielectric materials between the plates. In the construction we have used liquid Sr-90 with activity 100 mCi in cylindrical ampoule coiled up by thin film graphene as one plate and Manganase dioxide (MnO2) as other plate of the capacitor. A dielectric material (paper) is inserted between the plates. The high energetic beta particles from the Sr-90 penetrate graphene to produce ionization and then electrons are removed from graphene to dielectric material. Electrons inside the dielectric material cause polarization of dipoles. Consequently the radiation from the isotope produces an external current. We discuss effect of beta particles on dielectrics and electrodes beside advantage and disadvantage of a battery of this type.

Controlled thermal expansion printed wiring boards based on liquid crystal polymer dielectrics

NASA Technical Reports Server (NTRS)

Knoll, Thomas E.; Blizard, Kent; Jayaraj, K.; Rubin, Leslie S.

1994-01-01

Dielectric materials based on innovative Liquid Crystal Polymers (LCP's) have been used to fabricate surface mount printed wiring boards (PWB's) with a coefficient of thermal expansion matched to leadless ceramic chip carriers. Proprietary and patented polymer processing technology has resulted in self reinforcing material with balanced in-plane mechanical properties. In addition, LCP's possess excellent electrical properties, including a low dielectric constant (less than 2.9) and very low moisture absorption (less than 0.02%). LCP-based multilayer boards processed with conventional drilling and plating processes show improved performance over other materials because they eliminate the surface flatness problems of glass or aramid reinforcements. Laser drilling of blind vias in the LCP dielectric provides a very high density for use in direct chip attach and area array packages. The material is ideally suited for MCM-L and PCMCIA applications fabricated with very thin dielectric layers of the liquid crystal polymer.

Nanoindentation investigation of HfO2 and Al2O3 films grown by atomic layer deposition

Treesearch

K. Tapily; Joseph E. Jakes; D. S. Stone; P. Shrestha; D. Gu; H. Baumgart; A. A. Elmustafa

2008-01-01

The challenges of reducing gate leakage current and dielectric breakdown beyond the 45 nm technology node have shifted engineers’ attention from the traditional and proven dielectric SiO2 to materials of higher dielectric constant also known as high-k materials such as hafnium oxide (HfO2) and aluminum oxide (Al2O3). These high-k materials are projected to...

Tailorable Dielectric Material with Complex Permittivity Characteristics

NASA Technical Reports Server (NTRS)

Smith, Joseph G. (Inventor); Watson, Kent A. (Inventor); Elliott, Holly A (Inventor); Delozier, Donavon Mark (Inventor); Connell, John W. (Inventor); Ghose, Sayata (Inventor); Dudley, Kenneth L. (Inventor)

2014-01-01

A dielectric material includes a network of nanosubstrates, such as but not limited to nanotubes, nanosheets, or other nanomaterials or nanostructures, a polymer base material or matrix, and nanoparticles constructed at least partially of an elemental metal. The network has a predetermined nanosubstrate loading percentage by weight with respect to a total weight of the dielectric material, and a preferential or predetermined longitudinal alignment with respect to an orientation of an incident electrical field. A method of forming the dielectric material includes depositing the metal-based nanoparticles onto the nanosubstrates and subsequently mixing these with a polymer matrix. Once mixed, alignment can be achieved by melt extrusion or a similar mechanical shearing process. Alignment of the nanosubstrate may be in horizontal or vertical direction with respect to the orientation of an incident electrical field.

Sono-photocatalytic production of hydrogen by interface modified metal oxide insulators.

PubMed

Senevirathne, Rushdi D; Abeykoon, Lahiru K; De Silva, Nuwan L; Yan, Chang-Feng; Bandara, Jayasundera

2018-07-01

Dielectric oxide materials are well-known insulators that have many applications in catalysis as well as in device manufacturing industries. However, these dielectric materials cannot be employed directly in photochemical reactions that are initiated by the absorption of UV-Vis photons. Despite their insensitivity to solar energy, dielectric materials can be made sono-photoactive even for low energy IR photons by modifications of the interfacial properties of dielectric materials by noble metals and metal oxides. In this investigation, by way of interface modification of dielectric MgO nanoparticles by Ag metal and Ag 2 O nanoparticles, IR photon initiated sono-photocatalytic activity of MgO is reported. The observed photocatalytic activity is found to be the synergic action of both IR light and sonication effect and sonication assisted a multi-step, sub-bandgap excitation of electrons in the MgO is proposed for the observed catalytic activity of Ag/Ag 2 O coated MgO nanoparticles. Our investigation reveals that other dielectric materials such as silver coated SiO 2 and Al 2 O 3 also exhibit IR active sono-photocatalytic activity. Copyright © 2018 Elsevier B.V. All rights reserved.

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

Tooker, Angela C.; Felix, Sarah H.; Pannu, Satinderpall S.

A neural interface includes a first dielectric material having at least one first opening for a first electrical conducting material, a first electrical conducting material in the first opening, and at least one first interconnection trace electrical conducting material connected to the first electrical conducting material. A stiffening shank material is located adjacent the first dielectric material, the first electrical conducting material, and the first interconnection trace electrical conducting material.

A study of dynamic SIMS analysis of low-k dielectric materials

NASA Astrophysics Data System (ADS)

Mowat, Ian A.; Lin, Xue-Feng; Fister, Thomas; Kendall, Marius; Chao, Gordon; Yang, Ming Hong

2006-07-01

Dynamic SIMS is an established tool for the characterization of dielectric layers in semiconductors, both for contaminant levels and for composition. As the silicon-based semiconductor industry moves towards the use of copper rather than aluminum, there is also a need to use lower k-dielectric materials to reduce RC delays and to reduce cross-talk between closely spaced metal lines. New dielectric materials pose serious challenges for implementation into semiconductor processes and also for the analytical scientist doing measurements on them. The move from inorganic materials such as SiO 2 to organic or carbon-rich low-k materials is a large change for the SIMS analyst. Low-k dielectric films from different sources can be very different materials with different analytical issues. A SIMS challenge for these materials is dealing with their insulating nature and their also fragility, particularly for porous films. These materials can be extremely sensitive to electron beam damage during charge neutralization, leading to difficulties in determining depth scales and introducing unknown errors to secondary ion counts and their subsequent conversion to concentrations. This paper presents details regarding an investigation of the effects of electron beam exposure on a low-k material. These effects and their potential impact on SIMS data will be investigated using FT-IR, TOF-SIMS, AFM and stylus profilometry.

Metal-free magnetic conductor substrates for placement-immune antenna assemblies

DOEpatents

Eubanks, Travis Wayne; Loui, Hung; McDonald, Jacob Jeremiah

2015-09-29

A magnetic conductor substrate produced for mounting to an antenna includes a sheet of dielectric lattice material having a length, a width and a thickness that is less than the length and less than the width. Within the sheet of dielectric lattice material is disposed an array of dielectric elements.

From Organized High-Throughput Data to Phenomenological Theory using Machine Learning: The Example of Dielectric Breakdown

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

Kim, Chiho; Pilania, Ghanshyam; Ramprasad, Ramamurthy

Understanding the behavior (and failure) of dielectric insulators experiencing extreme electric fields is critical to the operation of present and emerging electrical and electronic devices. Despite its importance, the development of a predictive theory of dielectric breakdown has remained a challenge, owing to the complex multiscale nature of this process. We focus on the intrinsic dielectric breakdown field of insulators—the theoretical limit of breakdown determined purely by the chemistry of the material, i.e., the elements the material is composed of, the atomic-level structure, and the bonding. Starting from a benchmark dataset (generated from laborious first principles computations) of the intrinsicmore » dielectric breakdown field of a variety of model insulators, simple predictive phenomenological models of dielectric breakdown are distilled using advanced statistical or machine learning schemes, revealing key correlations and analytical relationships between the breakdown field and easily accessible material properties. Lastly, the models are shown to be general, and can hence guide the screening and systematic identification of high electric field tolerant materials.« less

Evolutionary search for new high-k dielectric materials: methodology and applications to hafnia-based oxides.

PubMed

Zeng, Qingfeng; Oganov, Artem R; Lyakhov, Andriy O; Xie, Congwei; Zhang, Xiaodong; Zhang, Jin; Zhu, Qiang; Wei, Bingqing; Grigorenko, Ilya; Zhang, Litong; Cheng, Laifei

2014-02-01

High-k dielectric materials are important as gate oxides in microelectronics and as potential dielectrics for capacitors. In order to enable computational discovery of novel high-k dielectric materials, we propose a fitness model (energy storage density) that includes the dielectric constant, bandgap, and intrinsic breakdown field. This model, used as a fitness function in conjunction with first-principles calculations and the global optimization evolutionary algorithm USPEX, efficiently leads to practically important results. We found a number of high-fitness structures of SiO2 and HfO2, some of which correspond to known phases and some of which are new. The results allow us to propose characteristics (genes) common to high-fitness structures--these are the coordination polyhedra and their degree of distortion. Our variable-composition searches in the HfO2-SiO2 system uncovered several high-fitness states. This hybrid algorithm opens up a new avenue for discovering novel high-k dielectrics with both fixed and variable compositions, and will speed up the process of materials discovery.

From Organized High-Throughput Data to Phenomenological Theory using Machine Learning: The Example of Dielectric Breakdown

DOE PAGES

Kim, Chiho; Pilania, Ghanshyam; Ramprasad, Ramamurthy

2016-02-02

Understanding the behavior (and failure) of dielectric insulators experiencing extreme electric fields is critical to the operation of present and emerging electrical and electronic devices. Despite its importance, the development of a predictive theory of dielectric breakdown has remained a challenge, owing to the complex multiscale nature of this process. We focus on the intrinsic dielectric breakdown field of insulators—the theoretical limit of breakdown determined purely by the chemistry of the material, i.e., the elements the material is composed of, the atomic-level structure, and the bonding. Starting from a benchmark dataset (generated from laborious first principles computations) of the intrinsicmore » dielectric breakdown field of a variety of model insulators, simple predictive phenomenological models of dielectric breakdown are distilled using advanced statistical or machine learning schemes, revealing key correlations and analytical relationships between the breakdown field and easily accessible material properties. Lastly, the models are shown to be general, and can hence guide the screening and systematic identification of high electric field tolerant materials.« less

Dielectric nanoresonators for light manipulation

NASA Astrophysics Data System (ADS)

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.

All-Dielectric Multilayer Cylindrical Structures for Invisibility Cloaking

PubMed Central

Mirzaei, Ali; Miroshnichenko, Andrey E.; Shadrivov, Ilya V.; Kivshar, Yuri S.

2015-01-01

We study optical response of all-dielectric multilayer structures and demonstrate that the total scattering of such structures can be suppressed leading to optimal invisibility cloaking. We use experimental material data and a genetic algorithm to reduce the total scattering by adjusting the material and thickness of various layers for several types of dielectric cores at telecommunication wavelengths. Our approach demonstrates 80-fold suppression of the total scattering cross-section by employing just a few dielectric layers. PMID:25858295

Dielectric particle injector for material processing

NASA Technical Reports Server (NTRS)

Leung, Philip L. (Inventor)

1992-01-01

A device for use as an electrostatic particle or droplet injector is disclosed which is capable of injecting dielectric particles or droplets. The device operates by first charging the dielectric particles or droplets using ultraviolet light induced photoelectrons from a low work function material plate supporting the dielectric particles or droplets, and then ejecting the charged particles or droplets from the plate by utilizing an electrostatic force. The ejected particles or droplets are mostly negatively charged in the preferred embodiment; however, in an alternate embodiment, an ion source is used instead of ultraviolet light to eject positively charged dielectric particles or droplets.

The Effect of Multi Wall Carbon Nanotubes on Some Physical Properties of Epoxy Matrix

NASA Astrophysics Data System (ADS)

Al-Saadi, Tagreed M.; hammed Aleabi, Suad; Al-Obodi, Entisar E.; Abdul-Jabbar Abbas, Hadeel

2018-05-01

This research involves using epoxy resin as a matrix for making a composite material, while the multi wall carbon nanotubes (MWNCTs) is used as a reinforcing material with different fractions (0.0,0.02, 0.04, 0.06) of the matrix weight. The mechanical ( hardness ), electrical ( dielectric constant, dielectric loss factor, dielectric strength, electrical conductivity ), and thermal properties (thermal conductivity ) were studied. The results showed the increase of hardness, thermal conductivity, electrical conductivity and break down strength with the increase of MWCNT concentration, but the behavior of dielectric loss factor and dielectric constant is opposite that.

Material with high dielectric constant, low dielectric loss, and good mechanical and thermal properties produced using multi-wall carbon nanotubes wrapped with poly(ether sulphone) in a poly(ether ether ketone) matrix

NASA Astrophysics Data System (ADS)

Zhang, Shuling; Wang, Hongsong; Wang, Guibin; Jiang, Zhenhua

2012-07-01

A material with high dielectric constant, low dielectric loss, and good mechanical and thermal properties was produced using multi-wall carbon nanotubes (MWCNTs) wrapped with poly(ether sulphone) (PES) dispersed in a poly(ether ether ketone) (PEEK) matrix. The material was fabricated using melt-blending, and MWCNT/PEEK composites show different degrees of improvement in the measured dielectric, mechanical, and thermal properties as compared to pure PEEK. This is attributed to the high conductivity of MWCNTs, the effect of wrapping MWCNTs with PES, the good dispersion of the wrapped MWCNTs in PEEK, and the strong interfacial adhesion between the wrapped MWCNTs and the PEEK.

Holmium hafnate: An emerging electronic device material

NASA Astrophysics Data System (ADS)

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

2015-03-01

We report structural, optical, charge transport, and temperature properties as well as the frequency dependence of the dielectric constant of Ho2Hf2O7 (HHO) which make this material desirable as an alternative high-k dielectric for future silicon technology devices. A high dielectric constant of ˜20 and very low dielectric loss of ˜0.1% are temperature and voltage independent at 100 kHz near ambient conditions. The Pt/HHO/Pt capacitor exhibits exceptionally low Schottky emission-based leakage currents. In combination with the large observed bandgap Eg of 5.6 eV, determined by diffuse reflectance spectroscopy, our results reveal fundamental physics and materials science of the HHO metal oxide and its potential application as a high-k dielectric for the next generation of complementary metal-oxide-semiconductor devices.

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

PubMed

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.

Recent Progress on Ferroelectric Polymer-Based Nanocomposites for High Energy Density Capacitors: Synthesis, Dielectric Properties, and Future Aspects.

PubMed

Prateek; Thakur, Vijay Kumar; Gupta, Raju Kumar

2016-04-13

Dielectric polymer nanocomposites are rapidly emerging as novel materials for a number of advanced engineering applications. In this Review, we present a comprehensive review of the use of ferroelectric polymers, especially PVDF and PVDF-based copolymers/blends as potential components in dielectric nanocomposite materials for high energy density capacitor applications. Various parameters like dielectric constant, dielectric loss, breakdown strength, energy density, and flexibility of the polymer nanocomposites have been thoroughly investigated. Fillers with different shapes have been found to cause significant variation in the physical and electrical properties. Generally, one-dimensional and two-dimensional nanofillers with large aspect ratios provide enhanced flexibility versus zero-dimensional fillers. Surface modification of nanomaterials as well as polymers adds flavor to the dielectric properties of the resulting nanocomposites. Nowadays, three-phase nanocomposites with either combination of fillers or polymer matrix help in further improving the dielectric properties as compared to two-phase nanocomposites. Recent research has been focused on altering the dielectric properties of different materials while also maintaining their superior flexibility. Flexible polymer nanocomposites are the best candidates for application in various fields. However, certain challenges still present, which can be solved only by extensive research in this field.

Study made of dielectric properties of promising materials for cryogenic capacitors

NASA Technical Reports Server (NTRS)

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

1967-01-01

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

Effect on the grain size of single-mode microwave sintered NiCuZn ferrite and zinc titanate dielectric resonator ceramics.

PubMed

Sirugudu, Roopas Kiran; Vemuri, Rama Krishna Murthy; Venkatachalam, Subramanian; Gopalakrishnan, Anisha; Budaraju, Srinivasa Murty

2011-01-01

Microwave sintering of materials significantly depends on dielectric, magnetic and conductive Losses. Samples with high dielectric and magnetic loss such as ferrites could be sintered easily. But low dielectric loss material such as dielectric resonators (paraelectrics) finds difficulty in generation of heat during microwave interaction. Microwave sintering of materials of these two classes helps in understanding the variation in dielectric and magnetic characteristics with respect to the change in grain size. High-energy ball milled Ni0.6Cu0.2Zn0.2Fe1.98O4-delta and ZnTiO3 are sintered in conventional and microwave methods and characterized for respective dielectric and magnetic characteristics. The grain size variation with higher copper content is also observed with conventional and microwave sintering. The grain size in microwave sintered Ni0.6Cu0.2Zn0.2Fe1.98O4-delta is found to be much small and uniform in comparison with conventional sintered sample. However, the grain size of microwave sintered sample is almost equal to that of conventional sintered sample of Ni0.3Cu0.5Zn0.2Fe1.98O4-delta. In contrast to these high dielectric and magnetic loss ferrites, the paraelectric materials are observed to sinter in presence of microwaves. Although microwave sintered zinc titanate sample showed finer and uniform grains with respect to conventional samples, the dielectric characteristics of microwave sintered sample are found to be less than that of conventional sample. Low dielectric constant is attributed to the low density. Smaller grain size is found to be responsible for low quality factor and the presence of small percentage of TiO2 is observed to achieve the temperature stable resonant frequency.

The possibility of giant dielectric materials for multilayer ceramic capacitors.

PubMed

Ishii, Tatsuya; Endo, Makoto; Masuda, Kenichiro; Ishida, Keisuke

2013-02-11

There have been numerous reports on discovery of giant dielectric permittivity materials called internal barrier layer capacitor in the recent years. We took particular note of one of such materials, i.e., BaTiO 3 with SiO 2 coating. It shows expressions of giant electric permittivity when processed by spark plasma sintering. So we evaluated various electrical characteristics of this material to find out whether it is applicable to multilayer ceramic capacitors. Our evaluation revealed that the isolated surface structure is the sole cause of expressions of giant dielectric permittivity.

Modeling and control of a dielectric elastomer actuator

NASA Astrophysics Data System (ADS)

Gupta, Ujjaval; Gu, Guo-Ying; Zhu, Jian

2016-04-01

The emerging field of soft robotics offers the prospect of applying soft actuators as artificial muscles in the robots, replacing traditional actuators based on hard materials, such as electric motors, piezoceramic actuators, etc. Dielectric elastomers are one class of soft actuators, which can deform in response to voltage and can resemble biological muscles in the aspects of large deformation, high energy density and fast response. Recent research into dielectric elastomers has mainly focused on issues regarding mechanics, physics, material designs and mechanical designs, whereas less importance is given to the control of these soft actuators. Strong nonlinearities due to large deformation and electromechanical coupling make control of the dielectric elastomer actuators challenging. This paper investigates feed-forward control of a dielectric elastomer actuator by using a nonlinear dynamic model. The material and physical parameters in the model are identified by quasi-static and dynamic experiments. A feed-forward controller is developed based on this nonlinear dynamic model. Experimental evidence shows that this controller can control the soft actuator to track the desired trajectories effectively. The present study confirms that dielectric elastomer actuators are capable of being precisely controlled with the nonlinear dynamic model despite the presence of material nonlinearity and electromechanical coupling. It is expected that the reported results can promote the applications of dielectric elastomer actuators to soft robots or biomimetic robots.

Celsian Glass-Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Dicarlo, James A.

1996-01-01

Glass-ceramic matrix reinforced fiber composite materials developed for use in low dielectric applications, such as radomes. Materials strong and tough, exhibit low dielectric properties, and endure high temperatures.

Colossal dielectric constant up to gigahertz at room temperature

NASA Astrophysics Data System (ADS)

Krohns, S.; Lunkenheimer, P.; Kant, Ch.; Pronin, A. V.; Brom, H. B.; Nugroho, A. A.; Diantoro, M.; Loidl, A.

2009-03-01

The applicability of recently discovered materials with extremely high ("colossal") dielectric constants, required for future electronics, suffers from the fact that their dielectric constant ɛ' only is huge in a limited frequency range below about 1 MHz. In the present report, we show that the dielectric properties of a charge-ordered nickelate, La15/8Sr1/8NiO4, surpass those of other materials. Especially, ɛ' retains its colossal magnitude of >10 000 well into the gigahertz range.

Fabrication of photonic band gap materials

DOEpatents

Constant, Kristen; Subramania, Ganapathi S.; Biswas, Rana; Ho, Kai-Ming

2002-01-15

A method for forming a periodic dielectric structure exhibiting photonic band gap effects includes forming a slurry of a nano-crystalline ceramic dielectric or semiconductor material and monodisperse polymer microspheres, depositing a film of the slurry on a substrate, drying the film, and calcining the film to remove the polymer microspheres therefrom. The film may be cold-pressed after drying and prior to calcining. The ceramic dielectric or semiconductor material may be titania, and the polymer microspheres may be polystyrene microspheres.

Encapsulation methods and dielectric layers for organic electrical devices

DOEpatents

Blum, Yigal D; Chu, William Siu-Keung; MacQueen, David Brent; Shi, Yijan

2013-07-02

The disclosure provides methods and materials suitable for use as encapsulation barriers and dielectric layers in electronic devices. In one embodiment, for example, there is provided an electroluminescent device or other electronic device with a dielectric layer comprising alternating layers of a silicon-containing bonding material and a ceramic material. The methods provide, for example, electronic devices with increased stability and shelf-life. The invention is useful, for example, in the field of microelectronic devices.

Nanostructure multilayer dielectric materials for capacitors and insulators

DOEpatents

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.

Nanostructure multilayer dielectric materials for capacitors and insulators

DOEpatents

Barbee, T.W. Jr.; Johnson, G.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. 1 fig.

Flexible neural interfaces with integrated stiffening shank

DOEpatents

Tooker, Angela C.; Felix, Sarah H.; Pannu, Satinderpall S.; Shah, Kedar G.; Sheth, Heeral; Tolosa, Vanessa

2016-07-26

A neural interface includes a first dielectric material having at least one first opening for a first electrical conducting material, a first electrical conducting material in the first opening, and at least one first interconnection trace electrical conducting material connected to the first electrical conducting material. A stiffening shank material is located adjacent the first dielectric material, the first electrical conducting material, and the first interconnection trace electrical conducting material.

Dielectric Characterization of Mylar and The Effects of Doping Processes.

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

Belcher, Cami Beth

2016-11-01

Mylar® polymer is a bi-axially oriented polyethylene terephthalate (PET) polymer film used widely as a dielectric, specifically in capacitors. The dielectric characteristics of Mylar have been well studied and documented over the years; however, many of the mechanisms responsible for dielectric breakdown and failure are not understood for modified versions of the material. Previous studies on Mylar confirm that factors such as temperature, humidity, and voltage ramp rates can also have a significant effect on the dielectric properties and measurement of the dielectric properties. This study seeks to determine how dielectric properties, including permittivity, dielectric loss, and breakdown strength, aremore » affected by doping of the polymer. To do this, two types of Mylar films, virgin film and film doped with a small-molecule electron-acceptor, are tested. Both types of materials are tested under a variety of environmental and experimental conditions, including testing at elevated temperatures, varying relative humidity, and varying ramp rates in dielectric breakdown testing. Analysis of permittivity, dielectric loss, and breakdown strength will be presented comparing virgin and doped Mylar to gain insight into the effects of doping with electron-acceptor molecules on dielectric properties under these varying environmental and test conditions.« less

Dielectric properties of biomass/biochar mixtures at microwave frequencies

USDA-ARS?s Scientific Manuscript database

Material dielectric properties are important for understanding their response to microwaves. Carbonaceous materials are considered good microwave absorbers and can be mixed with dry biomasses, which are otherwise low- loss materials, to improve the heating efficiency of biomass feedstocks. In this ...

High density circuit technology, part 4

NASA Technical Reports Server (NTRS)

Wade, T. E.

1982-01-01

An accurate study and evaluation of dielectric thin films is conducted in order to find the material or combination of materials which would optimize NASA'S double layer metal process. Emphasis is placed on polyimide dielectrics because of their reported outstanding dielectric characteristics (including electrical, chemical, thermal, and mechanical) and ease of processing, as well as their rapid acceptance by the semiconductor industry.

Microwave meter for rapid, nondestructive determination of in-shell peanut kernel moisture content from dielectric measurements on cleaned and uncleaned pod samples

USDA-ARS?s Scientific Manuscript database

Microwave Sensing provides a means for nondestructively determining the amount of moisture in materials by sensing the dielectric properties of the material. In this study, dielectric properties of Vidalia onions were analyzed for moisture dependence at 13.36 GHz and 23°C for moisture content betwee...

Dielectric characterization of high-performance spaceflight materials

NASA Astrophysics Data System (ADS)

Kleppe, Nathan Alan

As commercial space travel increases, the need for reliable structural health monitoring to predict possible weaknesses or failures of structural materials also increases. Monitoring of polymer-based materials may be achieved through the use of dielectric spectroscopy by comparing permittivity or conductivity measurements performed on a sample in use to that of a pristine sample. Changes in these measured values or of the relaxation frequencies, if present, can indicate chemical or physical changes occurring within the material and the possible need for maintenance/replacement. In this work, we established indicative trends that occur in the dielectric spectra during accelerated aging of various high-performance polymeric materials (EVOH, PEEK, PPS, and UHMWPE). Uses for these materials range from electrical insulation and protective coatings to windows and air- or space-craft parts that may be subject to environmental damage over long-term operation. Accelerated thermal aging and ultraviolet/water-spray cyclic aging were performed in order to investigate the degradation of the aforementioned material. The Havriliak-Negami model was used in the analysis of the measured dielectric spectra in order to obtain the characteristic fit parameters from which aging-related trends were identified. With reference to the literature and from measured FTIR spectra, observations were connected to the underlying mechanisms causing the dielectric relaxations.

Charging and breakdown in amorphous dielectrics: Phenomenological modeling approach and applications

NASA Astrophysics Data System (ADS)

Palit, Sambit

Amorphous dielectrics of different thicknesses (nm to mm) are used in various applications. Low temperature processing/deposition of amorphous thin-film dielectrics often result in defect-states or electronic traps. These traps are responsible for increased leakage currents and bulk charge trapping in many associated applications. Additional defects may be generated during regular usage, leading to electrical breakdown. Increased leakage currents, charge trapping and defect generation/breakdown are important and pervasive reliability concerns in amorphous dielectrics. We first explore the issue of charge accumulation and leakage in amorphous dielectrics. Historically, charge transport in amorphous dielectrics has been presumed, depending on the dielectric thickness, to be either bulk dominated (Frenkel-Poole (FP) emission) or contact dominated (Fowler-Nordheim tunneling). We develop a comprehensive dielectric charging modeling framework which solves for the transient and steady state charge accumulation and leakage currents in an amorphous dielectric, and show that for intermediate thickness dielectrics, the conventional assumption of FP dominated current transport is incorrect, and may lead to false extraction of dielectric parameters. We propose an improved dielectric characterization methodology based on an analytical approximation of our model. Coupled with ab-initio computed defect levels, the dielectric charging model explains measured leakage currents more accurately with lesser empiricism. We study RF-MEMS capacitive switches as one of the target applications of intermediate thickness amorphous dielectrics. To achieve faster analysis and design of RF-MEMS switches in particular, and electro-mechanical actuators in general, we propose a set of fundamental scaling relationships which are independent of specific physical dimensions and material properties; the scaling relationships provide an intrinsic classification of all electro-mechanical actuators. However, RF-MEMS capacitive switches are plagued by the reliability issue of temporal shifts of actuation voltages due to dielectric charge accumulation, often resulting in failure due to membrane stiction. Using the dielectric charging model, we show that in spite of unpredictable roughness of deposited dielectrics, there are predictable shifts in actuation voltages due to dielectric charging in RF-MEMS switches. We also propose a novel non-obtrusive, non-contact, fully electronic resonance based technique to characterize charging driven actuation shifts in RF-MEMS switches which overcomes limitations in conventionally used methods. Finally, we look into the issue of defect generation and breakdown in thick polymer dielectrics. Polymer materials often face premature electrical breakdown due to high electric fields and frequencies, and exposure to ambient humidity conditions. Using a field-driven correlated defect generation model, coupled with a model for temperature rise due to dielectric heating at AC stresses, we explain measured trends in time-to-breakdown and breakdown electric fields in polymer materials. Using dielectric heating we are able to explain the observed lifetime and dielectric strength reduction with increasing dielectric thicknesses. Performing lifetime measurements after exposure to controlled humidity conditions, we find that moisture ingress into a polymer material reduces activation barriers for chain breakage and increases dielectric heating. Overall, this thesis develops a comprehensive framework of dielectric charging, leakage and degradation of insulators of different thicknesses that have broad applications in multiple technologies.

Boron nitride as two dimensional dielectric: Reliability and dielectric breakdown

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

Ji, Yanfeng; Pan, Chengbin; Hui, Fei

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 untimelymore » 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.« less

PLZT capacitor and method to increase the dielectric constant

DOEpatents

Taylor, Ralph S.; Fairchild, Manuel Ray; Balachjandran, Uthamalingam; Lee, Tae H.

2017-12-12

A ceramic-capacitor includes a first electrically-conductive-layer, a second electrically-conductive-layer arranged proximate to the first electrically-conductive-layer, and a dielectric-layer interposed between the first electrically-conductive-layer and the second electrically-conductive-layer. The dielectric-layer is formed of a lead-lanthanum-zirconium-titanate material (PLZT), wherein the PLZT is characterized by a dielectric-constant greater than 125, when measured at 25 degrees Celsius and zero Volts bias, and an excitation frequency of ten-thousand Hertz (10 kHz). A method for increasing a dielectric constant of the lead-lanthanum-zirconium-titanate material (PLZT) includes the steps of depositing PLZT to form a dielectric-layer of a ceramic-capacitor, and heating the ceramic-capacitor to a temperature not greater than 300.degree. C.

The Charging of Composites in the Space Environment

NASA Technical Reports Server (NTRS)

Czepiela, Steven A.

1997-01-01

Deep dielectric charging and subsequent electrostatic discharge in composite materials used on spacecraft have become greater concerns since composite materials are being used more extensively as main structural components. Deep dielectric charging occurs when high energy particles penetrate and deposit themselves in the insulating material of spacecraft components. These deposited particles induce an electric field in the material, which causes the particles to move and thus changes the electric field. The electric field continues to change until a steady state is reached between the incoming particles from the space environment and the particles moving away due to the electric field. An electrostatic discharge occurs when the electric field is greater than the dielectric strength of the composite material. The goal of the current investigation is to investigate deep dielectric charging in composite materials and ascertain what modifications have to be made to the composite properties to alleviate any breakdown issues. A 1-D model was created. The space environment, which is calculated using the Environmental Workbench software, the composite material properties, and the electric field and voltage boundary conditions are input into the model. The output from the model is the charge density, electric field, and voltage distributions as functions of the depth into the material and time. Analysis using the model show that there should be no deep dielectric charging problem with conductive composites such as carbon fiber/epoxy. With insulating materials such as glass fiber/epoxy, Kevlar, and polymers, there is also no concern of deep dielectric charging problems with average day-to-day particle fluxes. However, problems can arise during geomagnetic substorms and solar particle events where particle flux levels increase by several orders of magnitude, and thus increase the electric field in the material by several orders of magnitude. Therefore, the second part of this investigation was an experimental attempt to measure the continuum electrical properties of a carbon fiber/epoxy composite, and to create a composite with tailorable conductivity without affecting its mechanical properties. The measurement of the conductivity and dielectric strength of carbon fiber/epoxy composites showed that these properties are surface layer dominated and difficult to measure. In the second experimental task, the conductivity of a glass fiber/epoxy composite was increased by 3 orders of magnitude, dielectric constant was increased approximately by a factor of 16, with minimal change to the mechanical properties, by adding conductive carbon black to the epoxy.

Moisture influence on the dielectric behavior of foods

USDA-ARS?s Scientific Manuscript database

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

Dielectric Performance of a High Purity HTCC Alumina at High Temperatures - a Comparison Study with Other Polycrystalline Alumina

NASA Technical Reports Server (NTRS)

Chen, Liangyu

2014-01-01

A very high purity (99.99+%) high temperature co-fired ceramic (HTCC) alumina has recently become commercially available. The raw material of this HTCC alumina is very different from conventional HTCC alumina, and more importantly there is no glass additive in this alumina material for co-firing processing. Previously, selected HTCC and LTCC (low temperature co-fired ceramic) alumina materials were evaluated at high temperatures as dielectric and compared to a regularly sintered 96% polycrystalline alumina (96% Al2O3), where 96% alumina was used as the benchmark. A prototype packaging system based on regular 96% alumina with Au thickfilm metallization successfully facilitated long term testing of high temperature silicon carbide (SiC) electronic devices for over 10,000 hours at 500 C. In order to evaluate this new high purity HTCC alumina for possible high temperature packaging applications, the dielectric properties of this HTCC alumina substrate were measured and compared with those of 96% alumina and a previously tested LTCC alumina from room temperature to 550 C at frequencies of 120 Hz, 1 KHz, 10 KHz, 100 KHz, and 1 MHz. A parallel-plate capacitive device with dielectric of the HTCC alumina and precious metal electrodes were used for measurements of the dielectric constant and dielectric loss of the co-fired alumina material in the temperature and frequency ranges. The capacitance and AC parallel conductance of the capacitive device were directly measured by an AC impedance meter, and the dielectric constant and parallel AC conductivity of the dielectric were calculated from the capacitance and conductance measurement results. The temperature and frequency dependent dielectric constant, AC conductivity, and dissipation factor of the HTCC alumina substrate are presented and compared to those of 96% alumina and a selected LTCC alumina. Other technical advantages of this new co-fired material for possible high packaging applications are also discussed.

Preliminary investigation of polystyrene/MoS{sub 2}-Oleylamine polymer composite for potential application as low-dielectric material in microelectronics

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

Landi, Giovanni, E-mail: glandi@unisa.it; Department of Industrial Engineering, University of Salerno, Via G. Paolo II 132, 84084 Fisciano; Altavilla, Claudia

2015-12-17

Insulating materials play a vital role in the design and performance of electrical systems for both steady and transient state conditions. Among the other properties, also in this field, polymer nanocomposites promise to offer exciting improvements. Many studies in the last decade has witnessed significant developments in the area of nano-dielectric materials and significant effects of nano-scale fillers on electric, thermal and mechanical properties of polymeric materials have been observed. However, the developments of new and advanced materials to be used the miniaturization of electronic devices fabrication require extensive studies on electrical insulation characteristics of these materials before they canmore » be used in commercial systems. In this work, Polystyrene (PS) composites were prepared by the blend solution method using MoS{sub 2}@Oleylamine nanosheets as filler. The dielectric properties of the resulting comoposite have been investigated at 300K and in the frequency range between 1000 Hz and 1 MHz. The addition of the MoS{sub 2}@Oleylamine nanosheets leads to a decreasing of the relative dielectric constant and of the electrical conductivity measured in the voltage range between ±500V. Thanks to a possibility to tune the electrical permittivity with the control of MoS{sub 2} concentration, these materials could be used as a low-dielectric material in the microelectronics applications.« less

Analytical scanning evanescent microwave microscope and control stage

DOEpatents

Xiang, Xiao-Dong; Gao, Chen; Duewer, Fred; Yang, Hai Tao; Lu, Yalin

2013-01-22

A scanning evanescent microwave microscope (SEMM) that uses near-field evanescent electromagnetic waves to probe sample properties is disclosed. The SEMM is capable of high resolution imaging and quantitative measurements of the electrical properties of the sample. The SEMM has the ability to map dielectric constant, loss tangent, conductivity, electrical impedance, and other electrical parameters of materials. Such properties are then used to provide distance control over a wide range, from to microns to nanometers, over dielectric and conductive samples for a scanned evanescent microwave probe, which enable quantitative non-contact and submicron spatial resolution topographic and electrical impedance profiling of dielectric, nonlinear dielectric and conductive materials. The invention also allows quantitative estimation of microwave impedance using signals obtained by the scanned evanescent microwave probe and quasistatic approximation modeling. The SEMM can be used to measure electrical properties of both dielectric and electrically conducting materials.

Analytical scanning evanescent microwave microscope and control stage

DOEpatents

Xiang, Xiao-Dong; Gao, Chen; Duewer, Fred; Yang, Hai Tao; Lu, Yalin

2009-06-23

A scanning evanescent microwave microscope (SEMM) that uses near-field evanescent electromagnetic waves to probe sample properties is disclosed. The SEMM is capable of high resolution imaging and quantitative measurements of the electrical properties of the sample. The SEMM has the ability to map dielectric constant, loss tangent, conductivity, electrical impedance, and other electrical parameters of materials. Such properties are then used to provide distance control over a wide range, from to microns to nanometers, over dielectric and conductive samples for a scanned evanescent microwave probe, which enable quantitative non-contact and submicron spatial resolution topographic and electrical impedance profiling of dielectric, nonlinear dielectric and conductive materials. The invention also allows quantitative estimation of microwave impedance using signals obtained by the scanned evanescent microwave probe and quasistatic approximation modeling. The SEMM can be used to measure electrical properties of both dielectric and electrically conducting materials.

Microwave measurement and modeling of the dielectric properties of vegetation

NASA Astrophysics Data System (ADS)

Shrestha, Bijay Lal

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

40 CFR 280.20 - Performance standards for new UST systems.

Code of Federal Regulations, 2010 CFR

2010-07-01

... protected in the following manner: (i) The tank is coated with a suitable dielectric material; (ii) Field... suitable dielectric material; (ii) Field-installed cathodic protection systems are designed by a corrosion...

40 CFR 280.20 - Performance standards for new UST systems.

Code of Federal Regulations, 2011 CFR

2011-07-01

... protected in the following manner: (i) The tank is coated with a suitable dielectric material; (ii) Field... suitable dielectric material; (ii) Field-installed cathodic protection systems are designed by a corrosion...

All 2D, high mobility, flexible, transparent thin film transistor

DOEpatents

Das, Saptarshi; Sumant, Anirudha V.; Roelofs, Andreas

2017-01-17

A two-dimensional thin film transistor and a method for manufacturing a two-dimensional thin film transistor includes layering a semiconducting channel material on a substrate, providing a first electrode material on top of the semiconducting channel material, patterning a source metal electrode and a drain metal electrode at opposite ends of the semiconducting channel material from the first electrode material, opening a window between the source metal electrode and the drain metal electrode, removing the first electrode material from the window located above the semiconducting channel material providing a gate dielectric above the semiconducting channel material, and providing a top gate above the gate dielectric, the top gate formed from a second electrode material. The semiconducting channel material is made of tungsten diselenide, the first electrode material and the second electrode material are made of graphene, and the gate dielectric is made of hexagonal boron nitride.

Diagnostics of Dielectric Materials with Several Relaxation Times

NASA Astrophysics Data System (ADS)

Karpov, A. G.; Klemeshev, V. A.

2018-04-01

A set of means for detection and preprocessing of dielectrometric information has been suggested for studying the polarization/depolarization of dielectrics. Special attention has been paid to the processing of dielectrometric data for inhomogeneous materials using dielectric diagrams. Rapid analysis has been carried out the results of which can be used as initial approximations in more accurate (more complicated and time-consuming) iterative algorithms for model fitting.

Dielectric properties of magnetorheological elastomers with different microstructure

NASA Astrophysics Data System (ADS)

Moucka, R.; Sedlacik, M.; Cvek, M.

2018-03-01

Composite materials containing magnetic particles organised within the polymer matrix by the means of an external magnetic field during the curing process were prepared, and their dielectric properties were compared with their isotropic analogues of the same filler concentration but homogeneous spatial distribution. A substantial dielectric response observed for anisotropic systems in a form of relaxation processes was explained as charge transport via the mechanism of variable range hopping. The changes in registered relaxations' critical frequency and shape of dielectric spectra with the filler concentration were discussed in terms of decreasing anisotropy of the system. The knowledge of the dielectric response of studied systems is essential for their practical applications such as piezoresistive sensors or radio-absorbing materials.

Colossal permittivity materials: Doping for superior dielectrics

NASA Astrophysics Data System (ADS)

Homes, Christopher C.; Vogt, Thomas

2013-09-01

The search for materials with colossal permittivity for use in capacitors has been met with limited success. A newly discovered co-doped titanium oxide material has an extremely high permittivity and negligible dielectric losses, and is likely to enable further scaling in electronic and energy-storage devices.

Giant Electrocaloric Effect in Ferroelectrics with Tailored Polaw-Nanostructures

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

Zhang, Qiming

2015-06-24

Electrocaloric effect (ECE) is the temperature and/or entropy change in a dielectric material caused by an electric field induced polarization change. Although ECE has been studied since 1930s, the very small ECE observed in earlier studies in bulk materials before 2007 makes it not attractive for practical cooling applications. The objectives of this DOE program are to carry out a systematical scientific research on the entropy change and ECE in polar-dielectrics, especially ferroelectrics based on several fundamental hypotheses and to search for answers on a few scientific questions. Especially, this research program developed a series of polar-dielectric materials with controlledmore » nano- and meso-structures and carried out studies on how these structures affect the polar-ordering, correlations, energy landscapes, and consequently the entropy states at different phases and ECE. The key hypotheses of the program include: (i) Whether a large ECE can be obtained near the ferroelectric-paraelectric (FE-PE) transition in properly designed ferroelectrics which possess large polarization P and large ß (the coefficient in the thermodynamic Landau theory where the Gibbs free energy G = G = G 0+ ½ a P 2 +1/4 b P 4 + 1/6 c P 6 – EP, and a = ß (T-T c), where b,c,ß and Tc are constants)? (ii) What determines/determine ß? Whether a ferroelectric material with built-in disorders, which disrupt the polar-correlations and enabling a large number of local polar-states, such as a properly designed ferroelectric relaxor, can achieve a large ECE? (iii) How to design a ferroelectric material which has flat energy landscape so that the energy barriers for switching among different phases are vanishingly small? What are the necessary conditions to maximize the number of coexisting phases? (iv) How to design ferroelectric materials with a large tunable dielectric response? That is, at zero electric field, the material possesses very low polar-correlation and hence a very small dielectric constant, under the application of electric field, the material develops long range polar-correlation and hence a high dielectric response. Studying and developing these materials will deepen our understanding on the polarization responses in strongly coupled materials and the roles of molecular and nano, meso-, and micro-scale defects and structures on the polarization responses. On the application front, besides ECE, these dielectrics will also have great impact on micro-electronics and communications. (v) The multi-field effect, besides the electric, elastic and even magnetic effects, could be made use of to tune the energy landscape of polar-materials and hence enhance the ECE. Hence the question is what are the suitable material systems to develop and maximize the multi-field effects? (vi) Besides solid dielectric, liquid dielectrics with properly designed molecular structures and dipolar coupling can also exhibit a large ECE near the dipolar order-disorder transition. The study of order-disorder transition and their influence on entropy change and ECE will provide additional avenue to study dielectrics and understand relationship between the polar-ordering and dipolar entropy in dielectrics. (vii) Besides the regular ECE in which applying an electric field will induce dipolar ordering, there are dielectric material systems which can exhibit negative ECE in which the applied field will reduce the dipolar ordering and anomalous ECE in which applying an electric field pulse will generate cooling only. The question is how to control and balance the nano- and meso-scale polar coupling in dielectrics to achieve such effects? ECE in dielectrics provides an interesting and effective avenue to probe the polar-correlation in dielectrics. Thus the study of ECE in polar-dielectrics, besides the application values, will also deepen our understanding of strongly coupled materials systems, phase transitions, and materials systems with nano- and meso-scale disorders. Through the efforts of this DoE program, we have developed understandings for many questions and materials approaches for many hypotheses listed above. The major accomplishments include: (i) The first one to show that a giant ECE can be obtained in bulk materials of ferroelectric P(VDF-TrFE) copolymer, which has a large ß coefficient and high polarization, near FE-PE transition.[1,3,12] (ii) The first who developed the theoretical analyses on the upper bound of dipolar entropy change in polar-materials and the general approach to maximize the coexisting phases with vanishingly small switching fields among the coexisting phases[10,23] Experimental results confirm these theoretical predictions.[24] (iii) The first to show that the relaxor ferroelectrics, due to built-in defects structures at nano- and meso scale, exhibit a giant ECE over a broad temperature range.[1,3,7,14] (iv) The first to show that a large ECE can be obtained near order-disorder transition in dielectric fluids such as liquid crystals with large dielectric anisotropy. Also the study developed a general approach for developing dielectric fluids to achieve a large electric field induced entropy change.[26] (v) We are starting to explore the multi-field effect (multiferroic effect) in nanocomposites in which there exist large dielectric contrasts between the matrix and nanofilelrs and showed that a significantly enhanced ECE compared with polymer matrix.[36] (vi) By facially tuning the nano- and meso-scale dipolar coupling, we are the first to show that an anomalous ECE can be obtained in a relaxor/normal ferroelectric blend.[39] (vii) Introduced and demonstrated that the internal bias field approach can be effective in enhancing the EC response at low electric field. The result is significant since for practical applications, a low applied field is highly desired. (viii) A high sensitivity ECE characterization system has been developed. This program has made major contributions to the advancement of the EC materials and understandings of EC phenomena. To reflect the advancement in the EC materials development and scientific understandings on ECE through in this time period (from Sept. 1, 2007 to May 2015), this final report is written based on the reports complied each year through the program. Some early works on the ECE which were obtained using the indirect method are not included in this report.« less

Theoretical and Numerical Approaches for Determining the Reflection and Transmission Coefficients of OPEFB-PCL Composites at X-Band Frequencies

PubMed Central

Ahmad, Ahmad F.; Abbas, Zulkifly; Obaiys, Suzan J.; Ibrahim, Norazowa; Hashim, Mansor; Khaleel, Haider

2015-01-01

Bio-composites of oil palm empty fruit bunch (OPEFB) fibres and polycaprolactones (PCL) with a thickness of 1 mm were prepared and characterized. The composites produced from these materials are low in density, inexpensive, environmentally friendly, and possess good dielectric characteristics. The magnitudes of the reflection and transmission coefficients of OPEFB fibre-reinforced PCL composites with different percentages of filler were measured using a rectangular waveguide in conjunction with a microwave vector network analyzer (VNA) in the X-band frequency range. In contrast to the effective medium theory, which states that polymer-based composites with a high dielectric constant can be obtained by doping a filler with a high dielectric constant into a host material with a low dielectric constant, this paper demonstrates that the use of a low filler percentage (12.2%OPEFB) and a high matrix percentage (87.8%PCL) provides excellent results for the dielectric constant and loss factor, whereas 63.8% filler material with 36.2% host material results in lower values for both the dielectric constant and loss factor. The open-ended probe technique (OEC), connected with the Agilent vector network analyzer (VNA), is used to determine the dielectric properties of the materials under investigation. The comparative approach indicates that the mean relative error of FEM is smaller than that of NRW in terms of the corresponding S21 magnitude. The present calculation of the matrix/filler percentages endorses the exact amounts of substrate utilized in various physics applications. PMID:26474301

Gas storage and separation by electric field swing adsorption

DOEpatents

Currier, Robert P; Obrey, Stephen J; Devlin, David J; Sansinena, Jose Maria

2013-05-28

Gases are stored, separated, and/or concentrated. An electric field is applied across a porous dielectric adsorbent material. A gas component from a gas mixture may be selectively separated inside the energized dielectric. Gas is stored in the energized dielectric for as long as the dielectric is energized. The energized dielectric selectively separates, or concentrates, a gas component of the gas mixture. When the potential is removed, gas from inside the dielectric is released.

Control of spontaneous emission of quantum dots using correlated effects of metal oxides and dielectric materials

NASA Astrophysics Data System (ADS)

Sadeghi, S. M.; Wing, W. J.; Gutha, R. R.; Capps, L.

2017-03-01

We study the emission dynamics of semiconductor quantum dots in the presence of the correlated impact of metal oxides and dielectric materials. For this we used layered material structures consisting of a base substrate, a dielectric layer, and an ultrathin layer of a metal oxide. After depositing colloidal CdSe/ZnS quantum dots on the top of the metal oxide, we used spectral and time-resolved techniques to show that, depending on the type and thickness of the dielectric material, the metal oxide can characteristically change the interplay between intrinsic excitons, defect states, and the environment, offering new material properties. Our results show that aluminum oxide, in particular, can strongly change the impact of amorphous silicon on the emission dynamics of quantum dots by balancing the intrinsic near band emission and fast trapping of carriers. In such a system the silicon/aluminum oxide charge barrier can lead to large variation of the radiative lifetime of quantum dots and control of the photo-ejection rate of electrons in quantum dots. The results provide unique techniques to investigate and modify physical properties of dielectrics and manage optical and electrical properties of quantum dots.

Control of spontaneous emission of quantum dots using correlated effects of metal oxides and dielectric materials.

PubMed

Sadeghi, S M; Wing, W J; Gutha, R R; Capps, L

2017-03-03

We study the emission dynamics of semiconductor quantum dots in the presence of the correlated impact of metal oxides and dielectric materials. For this we used layered material structures consisting of a base substrate, a dielectric layer, and an ultrathin layer of a metal oxide. After depositing colloidal CdSe/ZnS quantum dots on the top of the metal oxide, we used spectral and time-resolved techniques to show that, depending on the type and thickness of the dielectric material, the metal oxide can characteristically change the interplay between intrinsic excitons, defect states, and the environment, offering new material properties. Our results show that aluminum oxide, in particular, can strongly change the impact of amorphous silicon on the emission dynamics of quantum dots by balancing the intrinsic near band emission and fast trapping of carriers. In such a system the silicon/aluminum oxide charge barrier can lead to large variation of the radiative lifetime of quantum dots and control of the photo-ejection rate of electrons in quantum dots. The results provide unique techniques to investigate and modify physical properties of dielectrics and manage optical and electrical properties of quantum dots.

Dielectric Spectroscopy Analysis of Aged EVOH films with Application to Deterioration of Food Packaging Materials

NASA Astrophysics Data System (ADS)

Hoeller, Timothy

2007-06-01

Samples of EVOH films from compositions of 29 - 44 mol% ethylene content were exposed to thermal aging with and without light exposure. The results of Dielectric Spectroscopy on select samples showed Cole-Cole plots of skewed dielectric constant indicating multiple distributions of dipole relaxation times. The onset for decreases in dielectric response occurs earlier in samples exposed to elevated temperature under light exposure. Lower permittivity is exhibited in samples of higher ethylene content. Results from heat exposed samples are presented. Colorimetric analysis indicates only a slight film yellowing in one case. Raman spectroscopy on untreated films discerns changes in the C-C-O stretch associated with the alcohol. The effects of aging on microstructure may cause hindrance of molecular motion from moisture desorption. Slight material degradation occurs from film hardening presumably due to crosslinking. An electrical circuit model of the conduction processes associated with the EVOH films is presented. Dielectric analysis shows promise for monitoring material changes related to deterioration. We are also using these methods to understand Fluorescence Imaging which has been recently released for paper and plastic materials analysis. Future work may include refinement of these techniques for identification of changes in material properties correlated to packaging material barrier resistance.

Electrode/Dielectric Strip For High-Energy-Density Capacitor

NASA Technical Reports Server (NTRS)

Yen, Shiao-Ping S.

1994-01-01

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

Influence of Water Content on RF and Microwave Dielectric Behavior of Foods

USDA-ARS?s Scientific Manuscript database

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

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

USDA-ARS?s Scientific Manuscript database

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

Evaluation of high temperature capacitor dielectrics

NASA Astrophysics Data System (ADS)

Hammoud, Ahmad N.; Myers, Ira T.

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.

Evaluation of high temperature capacitor dielectrics

NASA Technical Reports Server (NTRS)

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.

Enhanced dielectric properties of Fe-substituted TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Ali, T.; Ahmed, Ateeq; Naseem siddique, M.; Tripathi, P.

2018-04-01

We report the structural and dielectric properties Ti1-xFexO2 (0.00 < x < 0.10) nanoparticles (NPs) synthesized by sol-gel method. The synthesized material has been characterized by soft X-ray absorption spectroscopy (SXAS) in order to investigate the fine structure and electronic valence state. SXAS analysis reveals that Fe-ions exist only in 3+ valance state in all the samples. The dielectric properties were studied by the use of LCR impedance spectroscopy. The dielectric constants, dielectric loss and A.C. conductivity have been determined as a function of frequency and composition of iron. At higher frequencies, the materials exhibited high AC Conductivity and low dielectric constant. The above theory could be explained by 'Maxwell Wagner Model' and may provide a new insight to fabricate nanomaterials having possible electrical application.

Tube-Super Dielectric Materials: Electrostatic Capacitors with Energy Density Greater than 200 J·cm−3

PubMed Central

Cortes, Francisco Javier Quintero; Phillips, Jonathan

2015-01-01

The construction and performance of a second generation of super dielectric material based electrostatic capacitors (EC), with energy density greater than 200 J·cm−3, which rival the best reported energy density of electric double layer capacitors (EDLC), also known as supercapacitors, are reported. The first generation super dielectric materials (SDM) are multi-material mixtures with dielectric constants greater than 1.0 × 105, composed of a porous, electrically insulating powder filled with a polarizable, ion-containing liquid. Second-generation SDMs (TSDM), introduced here, are anodic titania nanotube arrays filled with concentrated aqueous salt solutions. Capacitors using TiO2 based TSDM were found to have dielectric constants at ~0 Hz greater than 107 in all cases, a maximum operating voltage of greater than 2 volts and remarkable energy density that surpasses the highest previously reported for EC capacitors by approximately one order of magnitude. A simple model based on the classic ponderable media model was shown to be largely consistent with data from nine EC type capacitors employing TSDM. PMID:28793561

Tube-Super Dielectric Materials: Electrostatic Capacitors with Energy Density Greater than 200 J·cm-3.

PubMed

Cortes, Francisco Javier Quintero; Phillips, Jonathan

2015-09-17

The construction and performance of a second generation of super dielectric material based electrostatic capacitors (EC), with energy density greater than 200 J·cm - ³, which rival the best reported energy density of electric double layer capacitors (EDLC), also known as supercapacitors, are reported. The first generation super dielectric materials (SDM) are multi-material mixtures with dielectric constants greater than 1.0 × 10⁵, composed of a porous, electrically insulating powder filled with a polarizable, ion-containing liquid. Second-generation SDMs (TSDM), introduced here, are anodic titania nanotube arrays filled with concentrated aqueous salt solutions. Capacitors using TiO₂ based TSDM were found to have dielectric constants at ~0 Hz greater than 10⁷ in all cases, a maximum operating voltage of greater than 2 volts and remarkable energy density that surpasses the highest previously reported for EC capacitors by approximately one order of magnitude. A simple model based on the classic ponderable media model was shown to be largely consistent with data from nine EC type capacitors employing TSDM.

EDITORIAL: Special cluster on Dielectrics for Emerging Technologies

NASA Astrophysics Data System (ADS)

Clarke, R.; Youngs, I.; Stevens, G.

2004-02-01

The 2003 Conference on Dielectrics for Emerging Technologies was organised by the Institute of Physics Dielectrics Group as one of the participating conferences at the IOP Physics Congress held at Heriot-Watt University between 23 and 27 March 2003. This was the second annual conference of the new Dielectrics Group, which was formed from the former Dielectrics Society in October 2001. The conference policy remains unchanged, with the Group adopting an interdisciplinary and broadband approach to studies of the interaction of electromagnetic fields with materials. This policy is well exemplified by the papers that were delivered at this conference. The aims of the conference were three-fold: to provide a forum for the presentation of leading-edge research on emerging electromagnetic materials, to present developments on the use of dielectrics in emerging technologies and to broaden the debate on metamaterials in the UK, especially in relation to their potential applications. The metamaterials of interest here are macro- or meso-scopically structured materials that offer novel modes of electromagnetic field interaction, thereby widening the range of effective dielectric properties available to us for novel technological applications. They include `negative refractive index materials', `left handed materials', `photonic' or `electromagnetic band-gap materials' and actively-controlled or `smart' electromagnetic materials. Significant metamaterial applications are anticipated in the development of `perfect' lenses, filters, wavefront-conditioning layers and in improved metrology. The conference focussed additionally on dielectrics in support of electronics, photonics and optics, nano-materials, composites and structures, and the development of tuneable dielectrics and resonators for future applications in telecommunications. We are pleased to report that the conference was successful in achieving its objectives, thirty-four oral papers were delivered and twenty-three poster papers presented, many of which provoked significant debate. All contributions and the vigorous discussions held in this predominantly international forum testify to the health and vigour of this branch of materials physics and engineering. We were particularly pleased on this occasion to have the opportunity to run joint conference sessions with the `Structured Optical Materials' and `Electrostatics' conferences, which were run in parallel at the Congress. Electromagnetic materials science is inherently a cross-spectrum discipline and these sessions demonstrated the considerable overlap of technical interests and research from DC to optical frequencies. We are delighted to have the privilege of presenting eleven of the papers from the conference in this special cluster of Journal of Physics D: Applied Physics. Between them they capture the wide range of topics that were covered at the conference. The field of dielectric materials characterisation was well represented and amongst many other topics it included the study of nano-composites, represented here by the papers of Pelster et al and Hussain et al. Composite dielectrics at all scales lie at the centre of most new research into emerging applications and the paper by Bowler and that of Tuncer are also concerned with the understanding and characterisation of such materials. The understanding of the nature and distribution of space charge has always been a core dielectric study and a contribution to this field is made here by the paper of Marat-Mendes et al. Processing is a major factor that governs the properties of all dielectric materials---but this is particularly true in the case of sintered low-loss ceramics. The paper of Pullar et al adds to our knowledge in this important area. The remit of the conference led to the discussion of a very wide range of potential applications. One such is the use of dielectrophoretic forces for separating particles in suspensions (e.g. in pharmaceutical and diagnostic applications). The paper by Flores-Rodriguez and Markz presents a study on one aspect of this discipline. Presentations on meta- and structured materials at the conference are represented here in two papers: those of Shamonina and Solymar and of Zhou, Chan and Sheng, while a study in the closely allied area of band-gap materials is presented in the paper by Schuster and Klein. The final paper from the conference in this special cluster is concerned with an end-use application: the use of tuneable dielectric resonators in base-stations for future mobile telecoms networks. The paper by Krupka et al describes a magnetic approach to such tuning. In the longer term we sincerely hope that both the conference and these papers will prove to have made a significant contribution to the development and uses of dielectrics, and their metamaterial derivatives, in advanced technological applications. It is noteworthy that as a result of the success of this conference, the 2004 annual conference will be on the subject of `Dielectrics at Meso- and Nano-Scales'. We would like to take this opportunity to express our sincere thanks to all who participated in the conference for their contributions and we would like to express our particular thanks to the authors of the papers in this special cluster of Journal of Physics D: Applied Physics.

Low-Thermal-Expansion Filled Polytetrafluoroethylene

NASA Technical Reports Server (NTRS)

Shapiro, Sanford S.

1989-01-01

PTFE made thermally compatible with aluminum without changing dielectric constant. Manufactured with fillers and pores to reduce coefficient of thermal expansion by factor of 6 to match aluminum. Material retains 2.1 dielectric constant of pure PTFE. Combines filler and micropore concepts. Particles and voids embedded in PTFE matrix function cooperatively. Particles take up compressive stress imposed by contracting PTFE, and voids take up expanding material. Increases dielectric constant, while voids reduce it.

Pyroelectric Energy Harvesting: Model and Experiments

DTIC Science & Technology

2016-05-01

consisting of a current source for the pyroelectric current, a dielectric capacitor for the adiabatic charging and discharging, and optionally a resistor to...polarization) in a piezoelectric material. To extract work from the pyroelectric effect, the material acts as the dielectric in a capacitor that is...amplifier was chosen for the setup. The pyroelectric element is commonly modeled as a dielectric capacitor and a current source in parallel, as seen in

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

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

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

2013-11-15

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

Simultaneous Noncontact Precision Imaging of Microstructural and Thickness Variation in Dielectric Materials Using Terahertz Energy

NASA Technical Reports Server (NTRS)

Roth, Don J.; Seebo, Jeffrey P.; Winfree, William P.

2008-01-01

This article describes a noncontact single-sided terahertz electromagnetic measurement and imaging method that simultaneously characterizes microstructural (egs. spatially-lateral density) and thickness variation in dielectric (insulating) materials. The method was demonstrated for two materials-Space Shuttle External Tank sprayed-on foam insulation and a silicon nitride ceramic. It is believed that this method can be used as an inspection method for current and future NASA thermal protection system and other dielectric material inspection applications, where microstructural and thickness variation require precision mapping. Scale-up to more complex shapes such as cylindrical structures and structures with beveled regions would appear to be feasible.

Conducting nanotubes or nanostructures based composites, method of making them and applications

NASA Technical Reports Server (NTRS)

Gupta, Mool C. (Inventor); Yang, Yonglai (Inventor); Dudley, Kenneth L. (Inventor); Lawrence, Roland W. (Inventor)

2013-01-01

An electromagnetic interference (EMI) shielding material includes a matrix of a dielectric or partially conducting polymer, such as foamed polystyrene, with carbon nanotubes or other nanostructures dispersed therein in sufficient concentration to make the material electrically conducting. The composite is formed by dispersing the nanotube material in a solvent in which the dielectric or partially conducting polymer is soluble and mixing the resulting suspension with the dielectric or partially conducting polymer. A foaming agent can be added to produce a lightweight foamed material. An organometallic compound can be added to enhance the conductivity further by decomposition into a metal phase.

Artificial muscles of dielectric elastomers attached to artificial tendons of functionalized carbon fibers

NASA Astrophysics Data System (ADS)

Ye, Zhihang; Faisal, Md. Shahnewaz Sabit; Asmatulu, Ramazan; Chen, Zheng

2014-03-01

Dielectric elastomers are soft actuation materials with promising applications in robotics and biomedical de- vices. In this paper, a bio-inspired artificial muscle actuator with artificial tendons is developed for robotic arm applications. The actuator uses dielectric elastomer as artificial muscle and functionalized carbon fibers as artificial tendons. A VHB 4910 tape is used as the dielectric elastomer and PDMS is used as the bonding material to mechanically connect the carbon fibers to the elastomer. Carbon fibers are highly popular for their high electrical conductivities, mechanical strengths, and bio-compatibilities. After the acid treatments for the functionalization of carbon fibers (500 nm - 10 μm), one end of carbon fibers is spread into the PDMS material, which provides enough bonding strength with other dielectric elastomers, while the other end is connected to a DC power supply. To characterize the actuation capability of the dielectric elastomer and electrical conductivity of carbon fibers, a diaphragm actuator is fabricated, where the carbon fibers are connected to the actuator. To test the mechanical bonding between PDMS and carbon fibers, specimens of PDMS bonded with carbon fibers are fabricated. Experiments have been conducted to verify the actuation capability of the dielectric elastomer and mechanical bonding of PDMS with carbon fibers. The energy efficiency of the dielectric elastomer increases as the load increases, which can reach above 50%. The mechanical bonding is strong enough for robotic arm applications.

Compound surface-plasmon-polariton waves guided by a thin metal layer sandwiched between a homogeneous isotropic dielectric material and a structurally chiral material

NASA Astrophysics Data System (ADS)

Chiadini, Francesco; Fiumara, Vincenzo; Scaglione, Antonio; Lakhtakia, Akhlesh

2016-03-01

Multiple compound surface plasmon-polariton (SPP) waves can be guided by a structure consisting of a sufficiently thick layer of metal sandwiched between a homogeneous isotropic dielectric (HID) material and a dielectric structurally chiral material (SCM). The compound SPP waves are strongly bound to both metal/dielectric interfaces when the thickness of the metal layer is comparable to the skin depth but just to one of the two interfaces when the thickness is much larger. The compound SPP waves differ in phase speed, attenuation rate, and field profile, even though all are excitable at the same frequency. Some compound SPP waves are not greatly affected by the choice of the direction of propagation in the transverse plane but others are, depending on metal thickness. For fixed metal thickness, the number of compound SPP waves depends on the relative permittivity of the HID material, which can be useful for sensing applications.

Effective conductivity of wire mesh reflectors for space deployable antenna systems

NASA Technical Reports Server (NTRS)

Davis, William A.

1994-01-01

This report summarizes efforts to characterize the measurement of conductive mesh and smooth surfaces using proximity measurements for a dielectric resonator. The resonator operates in the HEM11 mode and is shown to have an evanescent field behavior in the vicinity of the sample surface, raising some question to the validity of measurements requiring near normal incidence on the material. In addition, the slow radial field decay outside of the dielectric resonator validates the sensitivity to the planar supporting structure and potential radiation effects. Though these concerns become apparent along with the sensitivity to the gap between the dielectric and the material surface, the basic concept of the material measurement using dielectric resonators has been verified for useful comparison of material surface properties. The properties, particularly loss, may be obtained by monitoring the resonant frequency along with the resonator quality factor (Q), 3 dB bandwidth, or the midband transmission amplitude. Comparison must be made to known materials to extract the desired data.

Hydrothermal synthesis of doped lanthanum zirconate nanomaterials and the effect of V–Ge substitution on their structural, electrical and dielectric properties

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

Farid, Muhammad Asim; Asghar, Muhammad Adnan; Ashiq, Muhammad Naeem, E-mail: naeemashiqqau@yahoo.com

2014-11-15

Graphical abstract: Variation of dielectric constant with frequency for all the synthesized materials. - Highlights: • Hydrothermal method has been successfully employed to synthesize the zirconates. • XRD confirmed the formation of required phase. • Increased electrical resistivity makes these materials useful for microwave devices. • Dielectric parameters of zirconates decrease with increasing frequency. • Dielectric constant decreases with increasing substituents concentration. - Abstract: A hydrothermal method was successfully employed for the synthesis of a series of vanadium and germanium co-doped pyrochlore lanthanum zirconates with composition La{sub 2−x}V{sub x}Zr{sub 2−y}Ge{sub y}O{sub 7} (where x, y = 0.0, 0.25, 0.50, 0.75more » and 1.0). The XRD and FTIR analyses confirmed the formation of single phase except vanadium and germanium substituted samples and the crystallite sizes are in the range of 7–31 nm for V{sup 3+}–Ge{sup 4+} substituted samples. The theoretical compositions are confirmed by the ED-XRF studies. The room temperature electrical resistivity increase with the substituents concentration which suggests that the synthesized materials can be used for microwave devices as such devices required highly resistive materials. Dielectric properties were measured in the frequency range of 6 kHz to 1 MHz. The dielectric parameters decrease with increase in frequency. The DC resistivity data is in good agreement with the dielectric data.« less

Microwave dielectric behavior of vegetation material

NASA Technical Reports Server (NTRS)

Elrayes, Mohamed A.; Ulaby, Fawwaz T.

1987-01-01

The microwave dielectric behavior of vegetation was examined through the development of theoretical models involving dielectric dispersion by both bound and free water and supported by extensive dielectric measurements conducted over a wide range of conditions. The experimental data were acquired using an open-ended coaxial probe that was developed for sensing the dielectric constant of thin layers of materials, such as leaves, from measurements of the complex reflection coefficient using a network analyzer. The probe system was successfully used to record the spectral variation of the dielectric constant over a wide frequency range extending from 0.5 to 20.4 GHz at numerous temperatures between -40 to +40 C. The vegetation samples were measured over a wide range of moisture conditions. To model the dielectric spectrum of the bound water component of the water included in vegetation, dielectric measurements were made for several sucrose-water solutions as analogs for the situation in vegetation. The results were used in conjunction with the experimental data for leaves to determine some of the constant coefficients in the theoretical models. Two models, both of which provide good fit to the data, are proposed.

Dielectric Heaters for Testing Spacecraft Nuclear Reactors

NASA Technical Reports Server (NTRS)

Sims, William Herbert; Bitteker, Leo; Godfroy, Thomas

2006-01-01

A document proposes the development of radio-frequency-(RF)-driven dielectric heaters for non-nuclear thermal testing of the cores of nuclear-fission reactors for spacecraft. Like the electrical-resistance heaters used heretofore for such testing, the dielectric heaters would be inserted in the reactors in place of nuclear fuel rods. A typical heater according to the proposal would consist of a rod of lossy dielectric material sized and shaped like a fuel rod and containing an electrically conductive rod along its center line. Exploiting the dielectric loss mechanism that is usually considered a nuisance in other applications, an RF signal, typically at a frequency .50 MHz and an amplitude between 2 and 5 kV, would be applied to the central conductor to heat the dielectric material. The main advantage of the proposal is that the wiring needed for the RF dielectric heating would be simpler and easier to fabricate than is the wiring needed for resistance heating. In some applications, it might be possible to eliminate all heater wiring and, instead, beam the RF heating power into the dielectric rods from external antennas.

Investigation of Fumed Silica/Aqueous NaCl Superdielectric Material.

PubMed

Jenkins, Natalie; Petty, Clayton; Phillips, Jonathan

2016-02-20

A constant current charge/discharge protocol which showed fumed silica filled to the point of incipient wetness with aqueous NaCl solution to have dielectric constants >10⁸ over the full range of dielectric thicknesses of 0.38-3.9 mm and discharge times of 0.25->100 s was studied, making this material another example of a superdielectric. The dielectric constant was impacted by both frequency and thickness. For time to discharge greater than 10 s the dielectric constant for all thicknesses needed to be fairly constant, always >10⁸, although trending higher with increasing thickness. At shorter discharge times the dielectric constant consistently decreased, with decreasing time to discharge. Hence, it is reasonable to suggest that for time to discharge >10 s the dielectric constant at all thicknesses will be greater than 10⁸. This in turn implies an energy density for a 5 micron thick dielectric layer in the order of 350 J/cm³ for discharge times greater than 10 s.

Investigation of Fumed Silica/Aqueous NaCl Superdielectric Material

PubMed Central

Jenkins, Natalie; Petty, Clayton; Phillips, Jonathan

2016-01-01

A constant current charge/discharge protocol which showed fumed silica filled to the point of incipient wetness with aqueous NaCl solution to have dielectric constants >108 over the full range of dielectric thicknesses of 0.38–3.9 mm and discharge times of 0.25–>100 s was studied, making this material another example of a superdielectric. The dielectric constant was impacted by both frequency and thickness. For time to discharge greater than 10 s the dielectric constant for all thicknesses needed to be fairly constant, always >109, although trending higher with increasing thickness. At shorter discharge times the dielectric constant consistently decreased, with decreasing time to discharge. Hence, it is reasonable to suggest that for time to discharge >10 s the dielectric constant at all thicknesses will be greater than 109. This in turn implies an energy density for a 5 micron thick dielectric layer in the order of 350 J/cm3 for discharge times greater than 10 s. PMID:28787918

Droplet Velocity Measurement Based on Dielectric Layer Thickness Variation Using Digital Microfluidic Devices.

PubMed

Zulkepli, Siti Noor Idora Syafinaz; Hamid, Nor Hisham; Shukla, Vineeta

2018-05-08

In recent years, the number of interdisciplinary research works related to the development of miniaturized systems with integrated chemical and biological analyses is increasing. Digital microfluidic biochips (DMFBs) are one kind of miniaturized systems designed for conducting inexpensive, fast, convenient and reliable biochemical assay procedures focusing on basic scientific research and medical diagnostics. The role of a dielectric layer in the digital microfluidic biochips is prominent as it helps in actuating microliter droplets based on the electrowetting-on-dielectric (EWOD) technique. The advantages of using three different material layers of dielectric such as parafilm, polytetrafluoroethylene (PTFE) and ethylene tetrafluoroethylene (ETFE) were reported in the current work. A simple fabrication process of a digital microfluidic device was performed and good results were obtained. The threshold of the actuation voltage was determined for all dielectric materials of varying thicknesses. Additionally, the OpenDrop device was tested by utilizing a single-plate system to transport microliter droplets for a bioassay operation. With the newly proposed fabrication methods, these dielectric materials showed changes in contact angle and droplet velocity when the actuation voltage was applied. The threshold actuation voltage for the dielectric layers of 10⁻13 μm was 190 V for the open plate DMFBs.

All-dielectric metamaterial frequency selective surface

NASA Astrophysics Data System (ADS)

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

Frequency selective surface (FSS) has been extensively studied due to its potential applications in radomes, antenna reflectors, high-impedance surfaces and absorbers. Recently, a new principle of designing FSS has been proposed and mainly studied in two levels. In the level of materials, dielectric materials instead of metallic patterns are capable of achieving more functional performance in FSS design. Moreover, FSSs made of dielectric materials can be used in different extreme environments, depending on their electrical, thermal or mechanical properties. In the level of design principle, the theory of metamaterial can be used to design FSS in a convenient and concise way. In this review paper, we provide a brief summary about the recent progress in all-dielectric metamaterial frequency selective surface (ADM-FSS). The basic principle of designing ADM-FSS is summarized. As significant tools, Mie theory and dielectric resonator (DR) theory are given which illustrate clearly how they are used in the FSS design. Then, several design cases including dielectric particle-based ADM-FSS and dielectric network-based ADM-FSS are introduced and reviewed. After a discussion of these two types of ADM-FSSs, we reviewed the existing fabrication techniques that are used in building the experiment samples. Finally, issues and challenges regarding the rapid fabrication techniques and further development aspects are discussed.

Synthesis and electromechanical characterization of a new acrylic dielectric elastomer with high actuation strain and dielectric strength

NASA Astrophysics Data System (ADS)

Hu, Wei; Niu, Xiaofan; Yang, Xinguo; Zhang, Naifang; Pei, Qibing

2013-04-01

Dielectric Elastomers (DEs) can be actuated under high electric field to produce large strains. Most high-performing DE materials such as the 3M™ VHB™ membranes are commercial products designed for industrial pressure-sensitive adhesives. The limited knowledge of the exact chemical structures of these commercial materials has made it difficult to understand the relationship between molecular structures and electromechanical properties. In this work, new acrylic elastomers based on n-butyl acrylate and acrylic acid were synthesized from monomer solutions by UV-initiated bulk polymerization. The new acrylic copolymers have a potential to obtain high dielectric constant, actuation strain, dielectric strength, and a high energy density. Silicone and ester oligomer diacrylates were also added onto the copolymer structures to suppress crystallization and to crosslink the polymer chains. Four acrylic formulations were developed with different amounts of acrylic acid. This gives a tunable stiffness, while the dielectric constant is varied from 4.3 to 7.1. The figure-of-merit performance of the best formulation is 186 % area strain, 222 MV/m of dielectric strength, and 2.7 MJ/m3 of energy density. To overcome electromechanical instability, different prestrain ratios were investigated, and under the optimized prestrain, the material has a lifetime of thousands of cycles at 120 % area strain.

Simultaneous observation of up/down conversion photoluminescence and colossal permittivity properties in (Er+Nb) co-doped TiO2 materials

NASA Astrophysics Data System (ADS)

Tse, Mei-Yan; Tsang, Ming-Kiu; Wong, Yuen-Ting; Chan, Yi-Lok; Hao, Jianhua

2016-07-01

We have investigated the optical and dielectric properties of rutile TiO2 doped with Nb and Er, i.e., (Er0.5Nb0.5)xTi1-xO2. The up/downconversion photoluminescence was observed in the visible and near-infrared region from the materials under 980 nm laser diode excitation. The upconversion emissions are attributed to the energy transfer between Er ions in the excited states. Moreover, the dielectric measurements indicate that the fabricated materials simultaneously present colossal permittivity properties with relatively low dielectric loss. Our work demonstrates the coexistence of both interesting luminescence and attractive dielectric characteristics in (Er+Nb) co-doped TiO2, showing the potential for multifunctional applications.

Metallic dielectric photonic crystals and methods of fabrication

DOEpatents

Chou, Jeffrey Brian; Kim, Sang-Gook

2017-12-05

A metallic-dielectric photonic crystal is formed with a periodic structure defining a plurality of resonant cavities to selectively absorb incident radiation. A metal layer is deposited on the inner surfaces of the resonant cavities and a dielectric material fills inside the resonant cavities. This photonic crystal can be used to selectively absorb broadband solar radiation and then reemit absorbed radiation in a wavelength band that matches the absorption band of a photovoltaic cell. The photonic crystal can be fabricated by patterning a sacrificial layer with a plurality of holes, into which is deposited a supporting material. Removing the rest of the sacrificial layer creates a supporting structure, on which a layer of metal is deposited to define resonant cavities. A dielectric material then fills the cavities to form the photonic crystal.

Metallic dielectric photonic crystals and methods of fabrication

DOEpatents

Chou, Jeffrey Brian; Kim, Sang-Gook

2016-12-20

A metallic-dielectric photonic crystal is formed with a periodic structure defining a plurality of resonant cavities to selectively absorb incident radiation. A metal layer is deposited on the inner surfaces of the resonant cavities and a dielectric material fills inside the resonant cavities. This photonic crystal can be used to selectively absorb broadband solar radiation and then reemit absorbed radiation in a wavelength band that matches the absorption band of a photovoltaic cell. The photonic crystal can be fabricated by patterning a sacrificial layer with a plurality of holes, into which is deposited a supporting material. Removing the rest of the sacrificial layer creates a supporting structure, on which a layer of metal is deposited to define resonant cavities. A dielectric material then fills the cavities to form the photonic crystal.

Super Dielectric Materials

PubMed Central

Fromille, Samuel; Phillips, Jonathan

2014-01-01

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. PMID:28788298

Super Dielectric Materials.

PubMed

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 (<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.

Laboratory simulation of irradiation-induced dielectric breakdown in spacecraft charging

NASA Technical Reports Server (NTRS)

Yadlowsky, E. J.; Churchill, R. J.; Hazelton, R. C.

1980-01-01

The discharging of dielectric samples irradiated by a beam of monoenergetic electrons is investigated. The development of a model, or models, which describe the discharge phenomena occuring on the irradiated dielectric targets is discussed. The electrical discharge characteristics of irradiated dielectric samples are discussed and the electrical discharge paths along dielectric surfaces and within the dielectric material are determined. The origin and destination of the surface emitted particles is examined and the charge and energy balance in the system is evaluated.

Elastomer modulus and dielectric strength scaling with sample thickness

NASA Astrophysics Data System (ADS)

Larson, Kent

2015-04-01

Material characteristics such as adhesion and dielectric strength have well recognized dependencies on material thickness. There is disagreement, however, on the scale: the long held dictum that dielectric strength is inversely proportional to the square root of sample thickness has been shown to not always hold true for all materials, nor for all possible thickness regions. In D-EAP applications some studies have postulated a "critical thickness" below which properties show significantly less thickness dependency. While a great deal of data is available for dielectric strength, other properties are not nearly as well documented as samples get thinner. In particular, elastic modulus has been found to increase and elongation to decrease as sample thickness is lowered. This trend can be observed experimentally, but has been rarely reported and certainly does not appear in typical suppliers' product data sheets. Both published and newly generated data were used to study properties such as elastic modulus and dielectric strength vs sample thickness in silicone elastomers. Several theories are examined to explain such behavior, such as the impact of defect size and of common (but not well reported) concentration gradients that occur during elastomer curing that create micron-sized layers at the upper and lower interfaces with divergent properties to the bulk material. As Dielectric Electro-Active Polymer applications strive to lower and lower material thickness, changing mechanical properties must be recognized and taken into consideration for accurate electro-mechanical predictions of performance.

Fluoro-polymer functionalized graphene for flexible ferroelectric polymer-based high-k nanocomposites with suppressed dielectric loss and low percolation threshold.

PubMed

Yang, Ke; Huang, Xingyi; Fang, Lijun; He, Jinliang; Jiang, Pingkai

2014-12-21

Flexible nanodielectric materials with high dielectric constant and low dielectric loss have huge potential applications in the modern electronic and electric industry. Graphene sheets (GS) and reduced-graphene oxide (RGO) are promising fillers for preparing flexible polymer-based nanodielectric materials because of their unique two-dimensional structure and excellent electrical and mechanical properties. However, the easy aggregation of GS/RGO significantly limits the potential of graphene in enhancing the dielectric constant of polymer composites. In addition, the poor filler/matrix nanoscale interfacial adhesion also causes difficulties in suppressing the dielectric loss of the composites. In this work, using a facile and environmentally friendly approach, polydopamine coated RGO (PDA-RGO) and fluoro-polymer functionalized RGO (PF-PDA-RGO) were prepared. Compared with the RGO prepared by the conventional methods [i.e. hydrazine reduced-graphene oxide (H-RGO)] and PDA-RGO, the resulting PF-PDA-RGO nanosheets exhibit excellent dispersion in the ferroelectric polymer matrix [i.e. poly(vinylidene fluoride-co-hexafluoro propylene), P(VDF-HFP)] and strong interfacial adhesion with the matrix, leading to a low percolation threshold (fc = 1.06 vol%) and excellent flexibility for the corresponding nanocomposites. Among the three nanocomposites, the P(VDF-HFP)/PF-PDA-RGO nanocomposites exhibited the optimum performance (i.e. simultaneously having high dielectric constant and low dielectric loss). For instance, at 1000 Hz, the P(VDF-HFP) nanocomposite sample with 1.0 vol% PF-PDA-RGO has a dielectric constant of 107.9 and a dielectric loss of 0.070, showing good potential for dielectric applications. Our strategy provides a new pathway to prepare high performance flexible nanodielectric materials.

Intrinsic Enhancement of Dielectric Permittivity in (Nb + In) co-doped TiO2 single crystals.

PubMed

Kawarasaki, Masaru; Tanabe, Kenji; Terasaki, Ichiro; Fujii, Yasuhiro; Taniguchi, Hiroki

2017-07-13

The development of dielectric materials with colossal permittivity is important for the miniaturization of electronic devices and fabrication of high-density energy-storage devices. The electron-pinned defect-dipoles has been recently proposed to boost the permittivity of (Nb + In) co-doped TiO 2 to 10 5 . However, the follow-up studies suggest an extrinsic contribution to the colossal permittivity from thermally excited carriers. Herein, we demonstrate a marked enhancement in the permittivity of (Nb + In) co-doped TiO 2 single crystals at sufficiently low temperatures such that the thermally excited carriers are frozen out and exert no influence on the dielectric response. The results indicate that the permittivity attains quadruple of that for pure TiO 2 . This finding suggests that the electron-pinned defect-dipoles add an extra dielectric response to that of the TiO 2 host matrix. The results offer a novel approach for the development of functional dielectric materials with large permittivity by engineering complex defects into bulk materials.

Absolute Thickness Measurements on Coatings Without Prior Knowledge of Material Properties Using Terahertz Energy

NASA Technical Reports Server (NTRS)

Roth, Don J.; Cosgriff, Laura M.; Harder, Bryan; Zhu, Dongming; Martin, Richard E.

2013-01-01

This study investigates the applicability of a novel noncontact single-sided terahertz electromagnetic measurement method for measuring thickness in dielectric coating systems having either dielectric or conductive substrate materials. The method does not require knowledge of the velocity of terahertz waves in the coating material. The dielectric coatings ranged from approximately 300 to 1400 m in thickness. First, the terahertz method was validated on a bulk dielectric sample to determine its ability to precisely measure thickness and density variation. Then, the method was studied on simulated coating systems. One simulated coating consisted of layered thin paper samples of varying thicknesses on a ceramic substrate. Another simulated coating system consisted of adhesive-backed Teflon adhered to conducting and dielectric substrates. Alumina samples that were coated with a ceramic adhesive layer were also investigated. Finally, the method was studied for thickness measurement of actual thermal barrier coatings (TBC) on ceramic substrates. The unique aspects and limitations of this method for thickness measurements are discussed.

Contact method to allow benign failure in ceramic capacitor having self-clearing feature

DOEpatents

Myers, John D; Taylor, Ralph S

2012-06-26

A capacitor exhibiting a benign failure mode has a first electrode layer, a first ceramic dielectric layer deposited on a surface of the first electrode, and a second electrode layer disposed on the ceramic dielectric layer, wherein selected areas of the ceramic dielectric layer have additional dielectric material of sufficient thickness to exhibit a higher dielectric breakdown voltage than the remaining majority of the dielectric layer. The added thickness of the dielectric layer in selected areas allows lead connections to be made at the selected areas of greater dielectric thickness while substantially eliminating a risk of dielectric breakdown and failure at the lead connections, whereby the benign failure mode is preserved.

Nuclear and Physical Properties of Dielectrics under Neutron Irradiation in Fast (BN-600) and Fusion (DEMO-S) Reactors

NASA Astrophysics Data System (ADS)

Blokhin, D. A.; Chernov, V. M.; Blokhin, A. I.

2017-12-01

Nuclear and physical properties (activation and transmutation of elements) of BN and Al2O3 dielectric materials subjected to neutron irradiation for up to 5 years in Russian fast (BN-600) and fusion (DEMO-S) reactors were calculated using the ACDAM-2.0 software complex for different post-irradiation cooling times (up to 10 years). Analytical relations were derived for the calculated quantities. The results may be used in the analysis of properties of irradiated dielectric materials and may help establish the rules for safe handling of these materials.

CMUTs with high-K atomic layer deposition dielectric material insulation layer.

PubMed

Xu, Toby; Tekes, Coskun; Degertekin, F

2014-12-01

Use of high-κ dielectric, atomic layer deposition (ALD) materials as an insulation layer material for capacitive micromachined ultrasonic transducers (CMUTs) is investigated. The effect of insulation layer material and thickness on CMUT performance is evaluated using a simple parallel plate model. The model shows that both high dielectric constant and the electrical breakdown strength are important for the dielectric material, and significant performance improvement can be achieved, especially as the vacuum gap thickness is reduced. In particular, ALD hafnium oxide (HfO2) is evaluated and used as an improvement over plasma-enhanced chemical vapor deposition (PECVD) silicon nitride (Six)Ny)) for CMUTs fabricated by a low-temperature, complementary metal oxide semiconductor transistor-compatible, sacrificial release method. Relevant properties of ALD HfO2) such as dielectric constant and breakdown strength are characterized to further guide CMUT design. Experiments are performed on parallel fabricated test CMUTs with 50-nm gap and 16.5-MHz center frequency to measure and compare pressure output and receive sensitivity for 200-nm PECVD Six)Ny) and 100-nm HfO2) insulation layers. Results for this particular design show a 6-dB improvement in receiver output with the collapse voltage reduced by one-half; while in transmit mode, half the input voltage is needed to achieve the same maximum output pressure.

Link between the dielectric properties of mesomorphic and biological materials

NASA Astrophysics Data System (ADS)

Szwajczak, Elzbieta; Szymanski, Aleksander B.

2002-06-01

An application of liquid crystalline materials as a model materials for the use in dielectric spectroscopy of the artificial biological materials and the tissues is discussed. It is shown that an application of the standard electrochemical concepts may break in the case of liquid crystalline materials as well as biological materials. The presence of space charge regions as well as electrical non- linearities of the sample may suggest some special possibility of the time domain technique application.

Flexoelectric effect in functionally graded materials: A numerical study

NASA Astrophysics Data System (ADS)

Kumar, Anuruddh; Kiran, Raj; Kumar, Rajeev; Chandra Jain, Satish; Vaish, Rahul

2018-04-01

The flexoelectric effect has been observed in a wide range of dielectric materials. However, the flexoelectric effect can only be induced using the strain gradient. Researchers have examined the flexoelectricity using non-uniform loading (cantilever type) or non-uniform shape in dielectric materials, which may be undesirable in many applications. In the present article, we demonstrate induced flexoelectricity in dielectric functionally graded materials (FGMs) due to non-uniform Youngs's modulus along the thickness. To examine flexoelectricity, Ba0.6Sr0.4TiO3 (BST) and polyvinylidene fluoride (PVDF) were used to numerically simulate the performance of FGMs. 2D simulation suggests that output voltage can drastically enhance for optimum grading index of FGMs.

Vapor etching of nuclear tracks in dielectric materials

DOEpatents

Musket, Ronald G.; Porter, John D.; Yoshiyama, James M.; Contolini, Robert J.

2000-01-01

A process involving vapor etching of nuclear tracks in dielectric materials for creating high aspect ratio (i.e., length much greater than diameter), isolated cylindrical holes in dielectric materials that have been exposed to high-energy atomic particles. The process includes cleaning the surface of the tracked material and exposing the cleaned surface to a vapor of a suitable etchant. Independent control of the temperatures of the vapor and the tracked materials provide the means to vary separately the etch rates for the latent track region and the non-tracked material. As a rule, the tracked regions etch at a greater rate than the non-tracked regions. In addition, the vapor-etched holes can be enlarged and smoothed by subsequent dipping in a liquid etchant. The 20-1000 nm diameter holes resulting from the vapor etching process can be useful as molds for electroplating nanometer-sized filaments, etching gate cavities for deposition of nano-cones, developing high-aspect ratio holes in trackable resists, and as filters for a variety of molecular-sized particles in virtually any liquid or gas by selecting the dielectric material that is compatible with the liquid or gas of interest.

Cellulose Triacetate Dielectric Films For Capacitors

NASA Technical Reports Server (NTRS)

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.

Rationally designed polyimides for high-energy density capacitor applications.

PubMed

Ma, Rui; Baldwin, Aaron F; Wang, Chenchen; Offenbach, Ido; Cakmak, Mukerrem; Ramprasad, Rampi; Sotzing, Gregory A

2014-07-09

Development of new dielectric materials is of great importance for a wide range of applications for modern electronics and electrical power systems. The state-of-the-art polymer dielectric is a biaxially oriented polypropylene (BOPP) film having a maximal energy density of 5 J/cm(3) and a high breakdown field of 700 MV/m, but with a limited dielectric constant (∼2.2) and a reduced breakdown strength above 85 °C. Great effort has been put into exploring other materials to fulfill the demand of continuous miniaturization and improved functionality. In this work, a series of polyimides were investigated as potential polymer materials for this application. Polyimide with high dielectric constants of up to 7.8 that exhibits low dissipation factors (<1%) and high energy density around 15 J/cm(3), which is 3 times that of BOPP, was prepared. Our syntheses were guided by high-throughput density functional theory calculations for rational design in terms of a high dielectric constant and band gap. Correlations of experimental and theoretical results through judicious variations of polyimide structures allowed for a clear demonstration of the relationship between chemical functionalities and dielectric properties.

Negative refraction in one- and two-dimensional lossless plasma dielectric photonic crystals

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

Guo, B.

2013-07-15

Negative refraction in one- and two-dimensional lossless plasma dielectric photonic crystals consisting of plasma and background materials is theoretically investigated and the necessary conditions for negative refraction in these two structures are obtained. The critical frequency ω{sub 0} and the bandwidth Δω for negative refraction are explored, and the parameter dependence of effects such as plasma filling factor and the dielectric constant of background materials is also examined and discussed.

Nonlinear Dynamics of Electroelastic Dielectric Elastomers

DTIC Science & Technology

2018-01-30

research will significantly advance the basic science and fundamental understanding of how rate- dependent material response couples to large, nonlinear...experimental studies of constrained dielectric elastomer films, a transition in the surface instability mechanism depending on the elastocapillary number...fundamental understanding of how rate- dependent material response couples to large, nonlinear material deformation under applied electrostatic loading to

Control of Silver Diffusion in Low-Temperature Co-Fired Diopside Glass-Ceramic Microwave Dielectrics

PubMed Central

Chou, Chen-Chia; Chang, Chun-Yao; Chen, Guang-Yu; Feng, Kuei-Chih; Tsao, Chung-Ya

2017-01-01

Electrode material for low-temperature co-fired diopside glass-ceramic used for microwave dielectrics was investigated in the present work. Diffusion of silver from the electrode to diopside glass-ceramics degrades the performance of the microwave dielectrics. Two approaches were adopted to resolve the problem of silver diffusion. Firstly, silicon-oxide (SiO2) powder was employed and secondly crystalline phases were chosen to modify the sintering behavior and inhibit silver ions diffusion. Nanoscale amorphous SiO2 powder turns to the quartz phase uniformly in dielectric material during the sintering process, and prevents the silver from diffusion. The chosen crystalline phase mixing into the glass-ceramics enhances crystallinity of the material and inhibits silver diffusion as well. The result provides a method to decrease the diffusivity of silver ions by adding the appropriate amount of SiO2 and appropriate crystalline ceramics in diopside glass-ceramic dielectric materials. Finally, we used IEEE 802.11a 5.8 GHz as target specification to manufacture LTCC antenna and the results show that a good broadband antenna was made using CaMgSi2O6 with 4 wt % silicon oxide. PMID:29286330

New calibration algorithms for dielectric-based microwave moisture sensors

USDA-ARS?s Scientific Manuscript database

New calibration algorithms for determining moisture content in granular and particulate materials from measurement of the dielectric properties at a single microwave frequency are proposed. The algorithms are based on identifying empirically correlations between the dielectric properties and the par...

Solid-State Ultracapacitor for Improved Energy Storage

NASA Technical Reports Server (NTRS)

Nabors, Sammy

2015-01-01

NASA's Marshall Space Flight Center has developed a solid-state ultracapacitor using a novel nanocomposite, dielectric material. The material's design is based on the internal barrier layer capacitance (IBLC) concept, and it uses novel dielectric and metallic conductive ink formulations. Novel processing methods developed by NASA provide for unique dielectric properties at the grain level. Nanoscale raw material powders are tailored using a variety of techniques and then formulated into a special ink. This dielectric ink is used with novel metallic conductive ink to print a capacitor layer structure into any design necessary to meet a range of technical requirements. The innovation is intended to replace current range safety batteries that NASA uses to power the systems that destroy off-course space vehicles. A solid-state design provides the needed robustness and safety for this demanding application.

Dielectric and Electromechanical Properties of Polyurethane and Polydimethylsiloxane Blends and their Nanocomposites

NASA Astrophysics Data System (ADS)

Cakmak, Enes

Conventional means of converting electrical energy to mechanical work are generally considered too noisy and bulky for many contemporary technologies such as microrobotic, microfluidic, and haptic devices. Dielectric electroactive polymers (D-EAPs) constitude a growing class of electroactive polymers (EAP) that are capable of producing mechanica work induced by an applied electric field. D-EAPs are considered remarkably efficient and well suited for a wide range of applications, including ocean-wave energy harvesters and prosthetic devices. However, the real-world application of D-EAPs is very limited due to a number of factors, one of which is the difficulty of producing high actuation strains at acceptably low electric fields. D-EAPs are elastomeric polymers and produce large strain response induced by external electric field. The electromechanical properties of D-EAPs depend on the dielectric properties and mechanical properties of the D-EAP. In terms of dielectric behavior, these actuators require a high dielectric constant, low dielectric loss, and high dielectric strength to produce an improved actuation response. In addition to their dielectric properties, the mechanical properties of D-EAPs, such as elastic moduli and hysteresis, are also of importance. Therefore, material properties are a key feature of D-EAP technology. DE actuator materials reported in the literature cover many types of elastomers and their composites formed with dielectric fillers. Along with polymeric matrix materials, various ceramic, metal, and organic fillers have been employed in enhancing dielectric behavior of DEs. This work describes an effort to characterize elastomer blends and composites of different matrix and dielectric polymer fillers according to their dielectric, mechanical, and electromechanical responses. This dissertation focuses on the development and characterization of polymer-polymer blends and composites from a high-k polyurethane (PU) and polydimethylsiloxane (PDMS) elastomers. Two different routes were followed with respect to elastomer processing: The first is a simple solution blending of the two types of elastomers, and the second is based on preparation of composites from PU nanofiber webs and PDMS elastomer. Both the blends and the nanofiber web composites showed improved dielectric and actuation characteristics.

Method for distributing chemicals through a fibrous material using low-headspace dielectric heating

DOEpatents

Banerjee, Sujit; Malcolm, Earl

2002-01-01

System and method for diffusing chemicals rapidly and evenly into and through fibrous material, such as wood. Chemicals are introduced into the fibrous material by applying the chemicals to the fibrous material. After treating the fibrous material with the chemicals, the fibrous material is maintained under low-headspace conditions. Thermal energy or dielectric heating, such as microwave or radio frequency energy, is applied to the fibrous material. As a result, the chemicals are able to distribute evenly and quickly throughout the fibrous material.

Measurement of the complex refractive index and complex dielectric permittivity of T.P.S. Space Shuttle tile materials at millimeter wavelengths

NASA Technical Reports Server (NTRS)

Afsar, Mohammed Nurul; Chi, Hua; Li, Xiaohui

1990-01-01

Complex refractive index and dielectric permittivity studies of presently used Space Shuttle tile materials at millimeter wavelengths reveal these tiles to exhibit similar absorption characteristics to those of fused silica materials. This absorption is mainly related to the water content in the specimen. A strong birefringence is observed at least in one of these fibrous refractory composite materials.

Super Dielectric Material Based Capacitors: Punched Membrane/Gel

NASA Astrophysics Data System (ADS)

Petty, C. W.; Phillips, J.

2018-05-01

Extensive testing showed, as predicted, that punched membranes, filled with a gel containing aqueous salt solutions, behave as superdielectric materials (SDM). Punched membrane superdielectrics employed herein consisted of a commercial cellulose based membrane material, Celgard 16 μ thick, a material frequently used as a separator material in supercapacitors, into which macroscopic holes (ca. 2.5 mm) were punched with a laser cutter, and the holes subsequently filled with a gel-like material composed of fumed silica, NaCl and water. The gross dielectric constants measured, generally > 105, and the energy densities, > 40 J/cm3 during slow discharge, were in the range expected for superdielectric materials. The measured capacitance and energy density tracked the number of holes punched/area filled with the dielectric gel. Also, the observed power law decrease in all parameters including energy, power and capacitance, followed the same trends observed in other classes of SDM. Control studies included testing dielectrics composed of Celgard into which no holes were punched, but the SDM gel spread, also produced values consistent with the SDM model: no measurable capacitance using the standard protocol. Finally, the values measured suggest these materials rival the energy density of some common battery types at low discharge rates, and surpass the best commercial supercapacitors at low discharge rates.

Origin of the colossal dielectric response of Pr0.6 Ca0.4 Mn O3

NASA Astrophysics Data System (ADS)

Biškup, N.; de Andrés, A.; Martinez, J. L.; Perca, C.

2005-07-01

We report the detailed study of dielectric response of Pr0.6Ca0.4MnO3 (PCMO), a member of the manganite family showing colossal magnetoresistance. Measurements have been performed on four polycrystalline samples and four single crystals, allowing us to compare and extract the essence of dielectric response in the material. High-frequency dielectric function is found to be ɛHF=30 , as expected for the perovskite material. Dielectric relaxation is found in the frequency window of 20Hzto1MHz at temperatures of 50-200K that yields to colossal low-frequency dielectric function, i.e., the static dielectric constant. The static dielectric constant is always colossal, but varies considerably in different samples from ɛ(0)=103to105 . The measured data can be simulated very well by blocking (surface barrier) capacitance in series with sample resistance. This indicates that the large dielectric constant in PCMO arises from the Schottky barriers at electrical contacts. Measurements in magnetic field and with dc bias support this interpretation. Colossal magnetocapacitance observed in the title compound is thus attributed to extrinsic effects. Weak anomaly at the charge ordering temperature can also be attributed to interplay of sample and contact resistance. We comment on our results in the framework of related studies by other groups.

Effects of BOX engineering on analogue/RF and circuit performance of InGaAs-OI-Si MOSFET

NASA Astrophysics Data System (ADS)

Maity, Subir Kr.; Pandit, Soumya

2017-11-01

InGaAs is an attractive choice as alternate channel material in n-channel metal oxide semiconductor transistor for high-performance applications. However, electrostatic integrity of such device is poor. In this paper, we present a comprehensive technology computer-aided design simulation-based study of the effect of scaling the thickness of the buried oxide (BOX) region and varying the dielectric constant of BOX material on the electrostatic integrity, analogue/radio frequency (RF) performance and circuit performance of InGaAs-on-Insulator device. Device with thin BOX layer gives better drain-induced barrier lowering performance which enhances output resistance. The carrier mobility remains almost constant with thinning of BOX layer up to certain value. By lowering the dielectric constant of the BOX material, it is further possible to improve the analogue and RF performance. Effect of BOX thickness scaling and role of BOX dielectric material on gain-frequency response of common source amplifier is also studied. It is observed that frequency response of the amplifier improves for thin BOX and with low dielectric constant-based material.

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

NASA Astrophysics Data System (ADS)

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.

Plasma polymerized high energy density dielectric films for capacitors

NASA Technical Reports Server (NTRS)

Yamagishi, F. G.

1983-01-01

High energy density polymeric dielectric films were prepared by plasma polymerization of a variety of gaseous monomers. This technique gives thin, reproducible, pinhole free, conformable, adherent, and insoluble coatings and overcomes the processing problems found in the preparation of thin films with bulk polymers. Thus, devices are prepared completely in a vacuum environment. The plasma polymerized films prepared all showed dielectric strengths of greater than 1000 kV/cm and in some cases values of greater than 4000 kV/cm were observed. The dielectric loss of all films was generally less than 1% at frequencies below 10 kHz, but this value increased at higher frequencies. All films were self healing. The dielectric strength was a function of the polymerization technique, whereas the dielectric constant varied with the structure of the starting material. Because of the thin films used (thickness in the submicron range) surface smoothness of the metal electrodes was found to be critical in obtaining high dielectric strengths. High dielectric strength graft copolymers were also prepared. Plasma polymerized ethane was found to be thermally stable up to 150 C in the presence of air and 250 C in the absence of air. No glass transitions were observed for this material.

Water and ion transport in ultra-adsorbing porous magnesium carbonate studied by dielectric spectroscopy

NASA Astrophysics Data System (ADS)

Pochard, Isabelle; Frykstrand, Sara; Ahlström, Olle; Forsgren, Johan; Strømme, Maria

2014-01-01

Porous materials are used in application areas ranging from drug and vaccine delivery, medical implants, molecular sieves and cosmetics to catalysis and humidity control. In the present work, we employed an alternative approach to gain in-depth understanding about water interaction properties in such materials by the use of dielectric spectroscopy and thereby show that it is possible to obtain information that is not accessible from the more commonly employed water interaction analysis techniques. Specifically, the complex dielectric response of Upsalite, a novel, super-hydroscopic, high-surface area, porous magnesium carbonate material was measured in isothermal frequency scans between 10-3 and 106 Hz at controlled relative humidity (RH). We found the dielectric constant of the dry material to be 1.82. The ratio of bound to free water present in Upsalite after adsorption at room temperature was found to be high irrespective of the surrounding humidity with values ranging from ˜67% to ˜90%. We further found that OH- ions are the charge carriers responsible for the electrode polarization observed in the dielectric response and that the amount of these ions that are free to move in the material corresponds to a concentration of the order of 1-10 μmol l-1 independent of RH. Finally, the OH- diffusion coefficient displayed a drastic decrease with decreasing RH, typical of transport in unsaturated conditions. The presented results provide detailed insight about water interactions in the novel water adsorbing material under study and it is foreseen that the employed analysis methods can be used to evaluate other types of moisture adsorbing materials as well as the movement of functional species in the pores of inorganic drug delivery materials and materials tailored for adsorption of harmful charged species.

Dielectric Properties of Ca0.7Bi0.3Ti0.7Cr0.3O3 (CBTC)-CaCu3Ti4O12 (CCTO) Composite

NASA Astrophysics Data System (ADS)

Mallmann, E. J. J.; Silva, M. A. S.; Sombra, A. S. B.; Botelho, M. A.; Mazzetto, S. E.; de Menezes, A. S.; Almeida, A. F. L.; Fechine, P. B. A.

2015-01-01

The main object of this work is to study two materials with giant dielectric constants: CaCu3Ti4O12 (CCTO) and Ca0.7Bi0.3Ti0.7Cr0.3O3 (CBTC). CBTC1- x -CCTO x composites were also obtained to create a new dielectric material with dielectric properties between these two phases. Structural properties were studied by x-ray powder diffraction (XRPD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and dielectric measurements. CCTO showed a cubic phase and CBTC an orthorhombic phase. An interesting result was that the dielectric constant ( K) did not follow the rule of the mixture of Lichtnecker, and this happened due to the presence of other phases of its crystalline structure, which decreases the value of K when compared to the predicted values of Lichtnecker. It was also found that the dielectric properties of the composite are very promising for use in microelectronics, according to the miniaturization factor, which is crucial for those applications.

Analysis of the possibilities of using dielectric foam in the construction of composite high voltage post-insulators

NASA Astrophysics Data System (ADS)

Mączka, T.; Paściak, G.; Jarski, A.; Piątek, M.

2016-02-01

This paper presents the construction and basic performance parameters of the innovative tubular construction of high voltage composite insulator filled with the lightweight foamed electroinsulating material. The possibility of using of the commercially available expanding foams for preparing the lightweight foamed dielectric materials was analysed. The expanding foams of silicone RTV and compositions based on epoxy resin and LSR silicone were taken into account. The lightweight foamed dielectric materials were prepared according to the own foaming technology. In this work the experimental results on the use of the selected foams for the preparing of the lightweight filling materials to the tubular structure of composite insulator of 110 kV are presented.

Processing Waveform-Based NDE

NASA Technical Reports Server (NTRS)

Roth, Donald J (Inventor)

2011-01-01

A computer implemented process for simultaneously measuring the velocity of terahertz electromagnetic radiation in a dielectric material sample without prior knowledge of the thickness of the sample and for measuring the thickness of a material sample using terahertz electromagnetic radiation in a material sample without prior knowledge of the velocity of the terahertz electromagnetic radiation in the sample is disclosed and claimed. Utilizing interactive software the process evaluates, in a plurality of locations, the sample for microstructural variations and for thickness variations and maps the microstructural and thickness variations by location. A thin sheet of dielectric material may be used on top of the sample to create a dielectric mismatch. The approximate focal point of the radiation source (transceiver) is initially determined for good measurements.

Using COMSOL Multiphysics Software to Model Anisotropic Dielectric and Metamaterial Effects in Folded-Waveguide Traveling-Wave Tube Slow-Wave Circuits

NASA Technical Reports Server (NTRS)

Starinshak, David P.; Smith, Nathan D.; Wilson, Jeffrey D.

2008-01-01

The electromagnetic effects of conventional dielectrics, anisotropic dielectrics, and metamaterials were modeled in a terahertz-frequency folded-waveguide slow-wave circuit. Results of attempts to utilize these materials to increase efficiency are presented.

Let's Measure the Dielectric Constant of a Piece of Paper!

ERIC Educational Resources Information Center

Karlow, Edwin A.

1991-01-01

Described is a simple circuit with which students can observe the effect of common dielectric materials in a capacitor and measure the dielectric constant of a piece of paper. Discussed are the theory, apparatus construction, and experimental procedures for this activity. (CW)

Role of copper in time dependent dielectric breakdown of porous organo-silicate glass low-k materials

NASA Astrophysics Data System (ADS)

Zhao, Larry; Pantouvaki, Marianna; Croes, Kristof; Tőkei, Zsolt; Barbarin, Yohan; Wilson, Christopher J.; Baklanov, Mikhail R.; Beyer, Gerald P.; Claeys, Cor

2011-11-01

The role of copper in time dependent dielectric breakdown (TDDB) of a porous low-k dielectric with TaN/Ta barrier was investigated on a metal-insulator-metal capacitor configuration where Cu ions can drift into the low-k film by applying a positive potential on the top while they are not permitted to enter the low-k dielectric if a negative potential is applied on the top. No difference in TDDB performance was observed between the positive and negative bias conditions, suggesting that Cu cannot penetrate TaN/Ta barrier to play a critical role in the TDDB of porous low-k material.

Reversible Phase Transition with Ultralarge Dielectric Relaxation Behaviors in Succinimide Lithium(I) Hybrids.

PubMed

Tang, Yun-Zhi; Wang, Bin; Zhou, Hai-Tao; Chen, Shao-Peng; Tan, Yu-Hui; Wang, Chang-Feng; Yang, Chang-Shan; Wen, He-Rui

2018-02-05

Dielectric relaxations have widely applied on high permittivity capacitors, dielectric switches, ferroelectrics, pyroelectrics, and electrical insulating materials. However, few investigations of large dielectric relaxation behaviors on organic-inorganic hybrid materials have been documented before. Here we present a novel two-dimensional succinimide lithium(I) hybrid compound, [Li(PDD) 2 ClO 4 ] n , 1, (PDD = 2,5-pyrrolidinedione = succinimide) which shows reversible phase transition behavior in the vicinity of 228 K accompanied by an unusual symmetry breaking from I4 1 /amd to C2/c. X-ray single crystal diffractions analysis indicates the twist motion of pyrrolidine heterocycles, and order-disorder motion of ClO 4 - anions triggered the reversible phase transition. By means of an intuitive crystallographic model (rattling ion model), we further illustrated the mechanism of the interesting reversible phase transition. Particularly, 1 shows ultralarge dielectric relaxation behavior in the vicinity of the phase transition by its dielectric constant dependence on temperatures and frequencies as well as its Cole-Cole relation.

Increase of dielectric constant in PVDF by incorporating La{sub 1.8}Sr{sub 0.2}NiO{sub 4} into its matrix

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

Kumar, Rajnish, E-mail: rajnish@iitp.ac.in; Goswami, Ashwin M., E-mail: ashwin.nanoplast@gmail.com; Kar, Manoranjan, E-mail: mano-iitg@yahoo.com

2016-05-06

To obtain the material with high dielectric constant and high dielectric strength for the technological applications, nanocomposite of Lanthanum Strontium Nickelete (La{sub 1.8}Sr{sub 0.2}NiO{sub 4}) as nanofiller and polyvinylidene fluoride (PVDF) as polymer matrix has been prepared. The different nanofiler weight concentration varies from 2-8 weight percent. X-ray diffraction technique confirms the phase formation of nanocomposite. Differential scanning calorimeter (DSC) has been employed to study the percentage of crystallinity and Impedance measurement has been carried out to study the dielectric constant. DSC analysis shows decreasing trend of crystallinity whereas impedance analysis gives increasing dielectric constant with increasing La{sub 1.8}Sr{sub 0.2}NiO{submore » 4} concentration in the nanocomposite. Also, these materials can be used as insulator in the transformer as the strength and dielectric behavior of present composite meets the technological requirements.« less

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

PubMed

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

2015-05-07

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

Ni-coated CaCu3Ti4O12/low density polyethylene composite material with ultra-high dielectric permittivity

NASA Astrophysics Data System (ADS)

Gao, L.; Wang, X.; Chen, Y.; Chi, Q. G.; Lei, Q. Q.

2015-08-01

We report a novel low-density polyethylene (LDPE) composite filled with nickel-coated CaCu3Ti4O12 ceramic (denoted as CCTO@Ni), prepared by a melt mixing technique, and its prominent dielectric characteristics. The effects of magnetic field treatment on the dielectric properties of CCTO@Ni/LDPE composite films with a low filler concentration of 10 vol.% were investigated. Our results show that the dielectric permittivity, loss tangent, and conductivity of the LDPE composite films initially improved and then decreased with increasing treatment time under the applied magnetic field. Magnetic field treatment for 60 min led to an ultra-high dielectric permittivity value of 1.57 × 104, four orders of magnitude higher than that of the pure LDPE material. Our results indicate that the magnetic treatment may have induced a percolation effect and enhanced the interfacial polarization of the CCTO@Ni/LDPE composite, resulting in the observed changes in its dielectric properties.

Crosslinked polyarylene ether nitrile film as flexible dielectric materials with ultrahigh thermal stability.

PubMed

Yang, Ruiqi; Wei, Renbo; Li, Kui; Tong, Lifen; Jia, Kun; Liu, Xiaobo

2016-11-09

Dielectric film with ultrahigh thermal stability based on crosslinked polyarylene ether nitrile is prepared and characterized. The film is obtained by solution-casting of polyarylene ether nitrile terminated phthalonitrile (PEN-Ph) combined with post self-crosslinking at high temperature. The film shows a 5% decomposition temperature over 520 °C and a glass transition temperature (T g ) around 386 °C. Stable dielectric constant and low dielectric loss are observed for this film in the frequency range of 100-200 kHz and in the temperature range of 25-300 °C. The temperature coefficient of dielectric constant is less than 0.001 °C -1 even at 400 °C. By cycling heating and cooling up to ten times or heating at 300 °C for 12 h, the film shows good reversibility and robustness of the dielectric properties. This crosslinked PEN film will be a potential candidate as high performance film capacitor electronic devices materials used at high temperature.

Crosslinked polyarylene ether nitrile film as flexible dielectric materials with ultrahigh thermal stability

NASA Astrophysics Data System (ADS)

Yang, Ruiqi; Wei, Renbo; Li, Kui; Tong, Lifen; Jia, Kun; Liu, Xiaobo

2016-11-01

Dielectric film with ultrahigh thermal stability based on crosslinked polyarylene ether nitrile is prepared and characterized. The film is obtained by solution-casting of polyarylene ether nitrile terminated phthalonitrile (PEN-Ph) combined with post self-crosslinking at high temperature. The film shows a 5% decomposition temperature over 520 °C and a glass transition temperature (Tg) around 386 °C. Stable dielectric constant and low dielectric loss are observed for this film in the frequency range of 100-200 kHz and in the temperature range of 25-300 °C. The temperature coefficient of dielectric constant is less than 0.001 °C-1 even at 400 °C. By cycling heating and cooling up to ten times or heating at 300 °C for 12 h, the film shows good reversibility and robustness of the dielectric properties. This crosslinked PEN film will be a potential candidate as high performance film capacitor electronic devices materials used at high temperature.

CMUTs with High-K Atomic Layer Deposition Dielectric Material Insulation Layer

PubMed Central

Xu, Toby; Tekes, Coskun; Degertekin, F. Levent

2014-01-01

Use of high-κ dielectric, atomic layer deposition (ALD) materials as an insulation layer material for capacitive micromachined ultrasonic transducers (CMUTs) is investigated. The effect of insulation layer material and thickness on CMUT performance is evaluated using a simple parallel plate model. The model shows that both high dielectric constant and the electrical breakdown strength are important for the dielectric material, and significant performance improvement can be achieved, especially as the vacuum gap thickness is reduced. In particular, ALD hafnium oxide (HfO2) is evaluated and used as an improvement over plasma-enhanced chemical vapor deposition (PECVD) silicon nitride (SixNy) for CMUTs fabricated by a low-temperature, complementary metal oxide semiconductor transistor-compatible, sacrificial release method. Relevant properties of ALD HfO2 such as dielectric constant and breakdown strength are characterized to further guide CMUT design. Experiments are performed on parallel fabricated test CMUTs with 50-nm gap and 16.5-MHz center frequency to measure and compare pressure output and receive sensitivity for 200-nm PECVD SixNy and 100-nm HfO2 insulation layers. Results for this particular design show a 6-dB improvement in receiver output with the collapse voltage reduced by one-half; while in transmit mode, half the input voltage is needed to achieve the same maximum output pressure. PMID:25474786

K-Band Latching Switches

NASA Technical Reports Server (NTRS)

Piotrowski, W. S.; Raue, J. E.

1984-01-01

Design, development, and tests are described for two single-pole-double-throw latching waveguide ferrite switches: a K-band switch in WR-42 waveguide and a Ka-band switch in WR-28 waveguide. Both switches have structurally simple junctions, mechanically interlocked without the use of bonding materials; they are impervious to the effects of thermal, shock, and vibration stresses. Ferrite material for the Ka-band switch with a proper combination of magnetic and dielectric properties was available and resulted in excellent low loss, wideband performance. The high power handling requirement of the K-band switch limited the choice of ferrite to nickel-zinc compositions with adequate magnetic properties, but with too low relative dielectric constant. The relative dielectric constant determines the junction dimensions for given frequency responses. In this case the too low value unavoidably leads to a larger than optimum junction volume, increasing the insertion loss and restricting the operating bandwidth. Efforts to overcome the materials-related difficulties through the design of a composite junction with increased effective dielectric properties efforts to modify the relative dielectric constant of nickel-zinc ferrite are examined.

GIANT DIELECTRIC TUNABLE BEHAVIOR OF Pr-DOPED SrTiO3 AT LOW TEMPERATURE

NASA Astrophysics Data System (ADS)

Wei, T.; Song, Q. G.; Zhou, Q. J.; Li, Z. P.; Chen, Y. F.; Qi, X. L.; Guo, S. Q.; Liu, J.-M.

2012-03-01

Contrast with conventional dielectric tunable materials such as barium strontium titanate (BST), here, we report one new dielectric tunable behavior for Sr1-xPrxTiO3 system at low temperature. Giant dielectric tunability is confirmed in this system. More importantly, the efficient dielectric tunability can be realized just using small bias field. In addition, critical threshold electric field is also confirmed. This phenomenon may be related with the competition interaction of polar state with quantum fluctuations.

Advanced concepts for transformers pressboard dielectric constant and mechanical strength

NASA Astrophysics Data System (ADS)

1982-03-01

Of the numerous electrical considerations in a material, the value of the dielectric constant serves as an important criterion in designing proper insulation systems. Ways to reduce the dielectric constant of solid (fibrous) insulating materials were investigated. A literature search was made on cellulosic and synthetic fibers and also additives which offered the potential for dielectric constant reduction of the solid insulation. Sample board structures were produced in the laboratory and tested for electrical, mechanical and chemical characteristics. Electrical tests determined the suitability of the material at transformer test and operating conditions. The mechanical tests established the physical characteristics of the modified board structures. Chemical tests checked the conductivity of the aqueous extract, acidity, and ash content. Further, compatibility with transformer oil and some aging tests were performed. An actual computer transformer design was made based on one of the modified board structures and the reduction in core steel and transformer losses were shown.

Effects of monoclinic symmetry on the properties of biaxial liquid crystals

NASA Astrophysics Data System (ADS)

Solodkov, Nikita V.; Nagaraj, Mamatha; Jones, J. Cliff

2018-04-01

Tilted smectic liquid crystal phases such as the smectic-C phase seen in calamitic liquid crystals are usually treated using the assumption of biaxial orthorhombic symmetry. However, the smectic-C phase has monoclinic symmetry, thereby allowing disassociation of the principal optic and dielectric axes based on symmetry and invariance principles. This is demonstrated here by comparing optical and dielectric measurements for two materials with highly first-order direct transitions from nematic to smectic-C phases. The results show a high difference between the orientations of the principal axes sets, which is interpreted as the existence of two distinct cone angles for optical and dielectric frequencies. Both materials exhibit an increasing degree of monoclinic behavior with decreasing temperature. Due to fast switching speeds, ferroelectric smectic-C* materials are important for fast modulators and LCoS devices, where the dielectric biaxiality influences device operation.

The Impact of Dielectric Material and Temperature on Dielectric Charging in RF MEMS Capacitive Switches

NASA Astrophysics Data System (ADS)

Papaioannou, George

The present work attempts to provide a better insight on the dielectric charging in RF-MEMS capacitive switches that constitutes a key issue limiting parameter of their commercialization. The dependence of the charging process on the nature of dielectric materials widely used in these devices, such as SiO2, Si3N4, AlN, Al2O3, Ta2O5, HfO2, which consist of covalent or ionic bonds and may exhibit piezoelectric properties is discussed taking into account the effect of deposition conditions and resulting material stoichiometry. Another key issue parameter that accelerates the charging and discharging processes by providing enough energy to trapped charges to be released and to dipoles to overcome potential barriers and randomize their orientation is the temperature will be investigated too. Finally, the effect of device structure will be also taken into account.

High Dielectric Low Loss Transparent Glass Material Based Dielectric Resonator Antenna with Wide Bandwidth Operation

NASA Astrophysics Data System (ADS)

Mehmood, Arshad; Zheng, Yuliang; Braun, Hubertus; Hovhannisyan, Martun; Letz, Martin; Jakoby, Rolf

2015-01-01

This paper presents the application of new high permittivity and low loss glass material for antennas. This glass material is transparent. A very simple rectangular dielectric resonator antenna is designed first with a simple microstrip feeding line. In order to widen the bandwidth, the feed of the design is modified by forming a T-shaped feeding. This new design enhanced the bandwidth range to cover the WLAN 5 GHz band completely. The dielectric resonator antenna cut into precise dimensions is placed on the modified microstrip feed line. The design is simple and easy to manufacture and also very compact in size of only 36 × 28 mm. A -10 dB impedance bandwidth of 18% has been achieved, which covers the frequency range from 5.15 GHz to 5.95 GHz. Simulations of the measured return loss and radiation patterns are presented and discussed.

Organic/Inorganic Nano-hybrids with High Dielectric Constant for Organic Thin Film Transistor Applications

NASA Astrophysics Data System (ADS)

Yu, Yang-Yen; Jiang, Ai-Hua; Lee, Wen-Ya

2016-11-01

The organic material soluble polyimide (PI) and organic-inorganic hybrid PI-barium titanate (BaTiO3) nanoparticle dielectric materials (IBX, where X is the concentration of BaTiO3 nanoparticles in a PI matrix) were successfully synthesized through a sol-gel process. The effects of various BaTiO3 contents on the hybrid film performance and performance optimization were investigated. Furthermore, pentacene-based organic thin film transistors (OTFTs) with PI-BaTiO3/polymethylmethacrylate or cyclic olefin copolymer (COC)-modified gate dielectrics were fabricated and examined. The hybrid materials showed effective dispersion of BaTiO3 nanoparticles in the PI matrix and favorable thermal properties. X-ray diffraction patterns revealed that the BaTiO3 nanoparticles had a perovskite structure. The hybrid films exhibited high formability and planarity. The IBX hybrid dielectric films exhibited tunable insulating properties such as the dielectric constant value and capacitance in ranges of 4.0-8.6 and 9.2-17.5 nF cm-2, respectively. Adding the modified layer caused the decrease of dielectric constant values and capacitances. The modified dielectric layer without cross-linking displayed a hydrophobic surface. The electrical characteristics of the pentacene-based OTFTs were enhanced after the surface modification. The optimal condition for the dielectric layer was 10 wt% hybrid film with the COC-modified layer; moreover, the device exhibited a threshold voltage of 0.12 V, field-effect mobility of 4.32 × 10-1 cm2 V-1 s-1, and on/off current of 8.4 × 107.

Optimization of shape control of a cantilever beam using dielectric elastomer actuators

NASA Astrophysics Data System (ADS)

Liu, Chong; Mao, Boyong; Huang, Gangting; Wu, Qichen; Xie, Shilin; Xu, Minglong

2018-05-01

Dielectric elastomer (DE) is a kind of smart soft material that has many advantages such as large deformation, fast response, lightweight and easy synthesis. These features make dielectric elastomer a suitable material for actuators. This article focuses on the shape control of a cantilever beam by using dielectric elastomer actuators. The shape control equation in finite element formulation of the cantilever beam partially covered with dielectric elastomer actuators is derived based on the constitutive equation of dielectric elastomer material by using Hamilton principle. The actuating forces produced by dielectric elastomer actuators depend on the number of layers, the position and the actuation voltage of dielectric elastomer actuators. First, effects of these factors on the shape control accuracy when one pair or multiple pairs of actuators are employed are simulated, respectively. The simulation results demonstrate that increasing the number of actuators or the number of layers can improve the control effect and reduce the actuation voltages effectively. Second, to achieve the optimal shape control effect, the position of the actuators and the drive voltages are all determined using a genetic algorithm. The robustness of the genetic algorithm is analyzed. Moreover, the implications of using one pair and multiple pairs of actuators to drive the cantilever beam to the expected shape are investigated. The results demonstrate that a small number of actuators with optimal placement and optimal voltage values can achieve the shape control of the beam effectively. Finally, a preliminary experimental verification of the control effect is carried out, which shows the correctness of the theoretical method.

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

PubMed

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

2016-09-21

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

Engineering Room-temperature Superconductors Via ab-initio Calculations

NASA Astrophysics Data System (ADS)

Gulian, Mamikon; Melkonyan, Gurgen; Gulian, Armen

The BCS, or bosonic model of superconductivity, as Little and Ginzburg have first argued, can bring in superconductivity at room temperatures in the case of high-enough frequency of bosonic mode. It was further elucidated by Kirzhnitset al., that the condition for existence of high-temperature superconductivity is closely related to negative values of the real part of the dielectric function at finite values of the reciprocal lattice vectors. In view of these findings, the task is to calculate the dielectric function for real materials. Then the poles of this function will indicate the existence of bosonic excitations which can serve as a "glue" for Cooper pairing, and if the frequency is high enough, and the dielectric matrix is simultaneously negative, this material is a good candidate for very high-Tc superconductivity. Thus, our approach is to elaborate a methodology of ab-initio calculation of the dielectric function of various materials, and then point out appropriate candidates. We used the powerful codes (TDDF with the DP package in conjunction with ABINIT) for computing dielectric responses at finite values of the wave vectors in the reciprocal lattice space. Though our report is concerned with the particular problem of superconductivity, the application range of the data processing methodology is much wider. The ability to compute the dielectric function of existing and still non-existing (though being predicted!) materials will have many more repercussions not only in fundamental sciences but also in technology and industry.

Improving the thermal stability and electrical parameters of a liquid crystalline material 4-n-(nonyloxy) benzoic acid by using Li ion beam irradiation

NASA Astrophysics Data System (ADS)

Kumar, Satendra; Verma, Rohit; Dwivedi, Aanchal; Dhar, R.; Tripathi, Ambuj

2018-05-01

Li ion beam irradiation studies on a liquid crystalline material 4-n-(nonyloxy) benzoic acid (NOBA) have been carried out. The material has phase sequence of I-N-SmC-Cr. Thermodynamic studies demonstrate that an irradiation fluence of 1×1013 ions-cm-2 results in the increased thermal stability of the smectic C (SmC) phase of the material. Dielectric measurements illustrate that the transverse component of the dielectric permittivity and hence the dielectric anisotropy of the material in the nematic (N) and SmC phases are increased as compared to those of the pure material due to irradiation. UV-Visible spectrum of the irradiated material shows an additional peak along with the peak of the pure material. The observed change in the thermodynamic and electrical parameters is attributed to the conversion of some of the dimers of NOBA to monomers of NOBA due to irradiation.

Coaxial-probe contact-force monitoring for dielectric properties measurements

USDA-ARS?s Scientific Manuscript database

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

Monitoring Coaxial-Probe Contact Force for Dielectric Properties Measurement

USDA-ARS?s Scientific Manuscript database

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

Effects of temperature and material on dielectric properties of pelleted wood-based biomass

USDA-ARS?s Scientific Manuscript database

The production of pelleted biomass represents a significant emerging industry in the United States. Solid biomass can be formed from the waste products of many different products. In this study, the effects of temperature and pellet material type on the dielectric properties were investigated. Tempe...

Dielectric properties of metallic alloy FeCoZr-dielectric ceramic PZT nanostructures prepared by ion sputtering in vacuum conditions

NASA Astrophysics Data System (ADS)

Boiko, O.

2018-05-01

The main objective of the research was investigation of dielectric properties of (FeCoZr)x(PZT)(100-x) granular nanocomposites and determination the influence of isochronous annealing in temperatures of 398 K-573 K on them. The impedance spectroscopy methodology was used. The measurements of electrical parameters, such as: phase shift angle φ, dielectric loss factor tgδ, capacity C and conductivity σ of (FeCoZr)x(PZT)(100-x) nanocomposites have been performed. Frequency dependencies of these parameters were obtained for the ambient temperature range 98 K-373 K for the frequencies ranging from 50 Hz to 105 Hz. It was established, that the conductivity σ of the tested materials before the percolation threshold demonstrates non-linear dependence on frequency. Furthermore, it increases when the ambient temperature is increasing, which indicates a dielectric type of the material. The two types of electrical conduction: capacitive (phase shift angle φ takes negative values) and inductive (φ takes positive values) have been observed. It was concluded that the hopping conductivity dominated in the nanocomposites. Voltage and current resonances phenomena are observed in the materials. The isochronous annealing intensifies the dielectric properties of (FeCoZr)x(PZT)(100-x) nanocomposites.

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

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

Dai, Steven Xunhu; Hsieh, Lung-Hwa.

2012-04-01

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

Nonlinear dielectric effects in liquids: a guided tour

NASA Astrophysics Data System (ADS)

Richert, Ranko

2017-09-01

Dielectric relaxation measurements probe how the polarization of a material responds to the application of an external electric field, providing information on structure and dynamics of the sample. In the limit of small fields and thus linear response, such experiments reveal the properties of the material in the same thermodynamic state it would have in the absence of the external field. At sufficiently high fields, reversible changes in enthalpy and entropy of the system occur even at constant temperature, and these will in turn alter the polarization responses. The resulting nonlinear dielectric effects feature field induced suppressions (saturation) and enhancements (chemical effect) of the amplitudes, as well as time constant shifts towards faster (energy absorption) and slower (entropy reduction) dynamics. This review focuses on the effects of high electric fields that are reversible and observed at constant temperature for single component glass-forming liquids. The experimental challenges involved in nonlinear dielectric experiments, the approaches to separating and identifying the different sources of nonlinear behavior, and the current understanding of how high electric fields affect dielectric materials will be discussed. Covering studies from Debye’s initial approach to the present state-of-the-art, it will be emphasized what insight can be gained from the nonlinear responses that are not available from dielectric relaxation results obtained in the linear regime.

Development of Dielectric Material with Ceramic Matrix Composite (CMC) Produced from Kaolinite and CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO)

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

Yin, Wong Swee; Hassan, Jumiah; Hashim, Mansor

Ceramic matrix composites (CMC) combine reinforcing ceramic phases, CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) with a ceramic matrix, kaolinite to create materials with new and superior properties. 10% and 20% CCTO were prepared by using a conventional solid state reaction method. CMC samples were pre-sintered at 800 deg. C and sintered at 1000 deg. C. The dielectric properties of samples were measured using HP 4192A LF Impedance Analyzer. Microstructures of the samples were observed using an optical microscope. XRD was used to determine the crystalline structure of the samples. The AFM showed the morphology of the samples. The results showed thatmore » the dielectric constant and dielectric loss factor of both samples are frequency dependent. At 10 Hz, the dielectric constant is 10{sup 11} for both samples. The CMC samples were independent with temperature with low dielectric constant in the frequency range of 10{sup 4}-10{sup 6} Hz. Since the CMC samples consist of different amount of kaolinite, so each sample exhibit different defect mechanism. Different reaction may occur for different composition of material. The effects of processing conditions on the microstructure and electrical properties of CMC are also discussed.« less

Characterizing dielectric tensors of anisotropic materials from a single measurement

NASA Astrophysics Data System (ADS)

Smith, Paula Kay

Ellipsometry techniques look at changes in polarization states to measure optical properties of thin film materials. A beam reflected from a substrate measures the real and imaginary parts of the index of the material represented as n and k, respectively. Measuring the substrate at several angles gives additional information that can be used to measure multilayer thin film stacks. However, the outstanding problem in standard ellipsometry is that it uses a limited number of incident polarization states (s and p). This limits the technique to isotropic materials. The technique discussed in this paper extends the standard process to measure anisotropic materials by using a larger set of incident polarization states. By using a polarimeter to generate several incident polarization states and measure the polarization properties of the sample, ellipsometry can be performed on biaxial materials. Use of an optimization algorithm in conjunction with biaxial ellipsometry can more accurately determine the dielectric tensor of individual layers in multilayer structures. Biaxial ellipsometry is a technique that measures the dielectric tensors of a biaxial substrate, single-layer thin film, or multi-layer structure. The dielectric tensor of a biaxial material consists of the real and imaginary parts of the three orthogonal principal indices (n x + ikx, ny +iky and nz + i kz) as well as three Euler angles (alpha, beta and gamma) to describe its orientation. The method utilized in this work measures an angle-of-incidence Mueller matrix from a Mueller matrix imaging polarimeter equipped with a pair of microscope objectives that have low polarization properties. To accurately determine the dielectric tensors for multilayer samples, the angle-of-incidence Mueller matrix images are collected for multiple wavelengths. This is done in either a transmission mode or a reflection mode, each incorporates an appropriate dispersion model. Given approximate a priori knowledge of the dielectric tensor and film thickness, a Jones reflectivity matrix is calculated by solving Maxwell's equations at each surface. Converting the Jones matrix into a Mueller matrix provides a starting point for optimization. An optimization algorithm then finds the best fit dielectric tensor based on the measured angle-of-incidence Mueller matrix image. This process can be applied to polarizing materials, birefringent crystals and the multilayer structures of liquid crystal displays. In particular, the need for such accuracy in liquid crystal displays is growing as their applications in industry evolve.

Effects of synthesis techniques on chemical composition, microstructure and dielectric properties of Mg-doped calcium titanate

NASA Astrophysics Data System (ADS)

Jongprateep, Oratai; Sato, Nicha

2018-04-01

Calcium titanate (CaTiO3) has been recognized as a material for fabrication of dielectric components, owing to its moderate dielectric constant and excellent microwave response. Enhancement of dielectric properties of the material can be achieved through doping, compositional and microstructural control. This study, therefore, aimed at investigating effects of powder synthesis techniques on compositions, microstructure, and dielectric properties of Mg-doped CaTiO3. Solution combustion and solid-state reaction were powder synthesis techniques employed in preparation of undoped CaTiO3 and CaTiO3 doped with 5-20 at% Mg. Compositional analysis revealed that powder synthesis techniques did not exhibit a significant effect on formation of secondary phases. When Mg concentration did not exceed 5 at%, the powders prepared by both techniques contained only a single phase. An increase of MgO secondary phase was observed as Mg concentrations increased from 10 to 20 at%. Experimental results, on the contrary, revealed that powder synthesis techniques contributed to significant differences in microstructure. Solution combustion technique produced powders with finer particle sizes, which consequently led to finer grain sizes and density enhancement. High-density specimens with fine microstructure generally exhibit improved dielectric properties. Dielectric measurements revealed that dielectric constants of all samples ranged between 231 and 327 at 1 MHz, and that superior dielectric constants were observed in samples prepared by the solution combustion technique.

Review of the role of dielectric anisotropy in Dyakonov surface-wave propagation

NASA Astrophysics Data System (ADS)

Nelatury, Sudarshan R., II; Polo, John A., Jr.; Lakhtakia, Akhlesh

2008-08-01

Surface waves (SWs) are localized waves that travel along the planar interface between two different mediums when certain dispersion relations are satisfied. If both mediums have purely dielectric constitutive properties, the characteristics of SW propagation are determined by the anisotropy of both mediums. Surface waves are then called Dyakonov SWs (DSWs), after Dyakonov who theoretically established the possibility of SW propagation at the planar interface of an isotropic dielectric and a positive uniaxial dielectric. Since then, DSW propagation guided by interfaces between a variety of dielectrics has been studied. With an isotropic dielectric on one side, the dielectric on the other side of the interface can be not only positive uniaxial but also biaxial. DSW propagation can also occur along an interface between two uniaxial or biaxial dielectrics that are twisted about a common axis with respect to each other but are otherwise identical. Recently, DSW propagation has been studied taking (i) uniaxial dielectrics such as calomel and dioptase crystals; (ii) biaxial dielectrics such as hemimorphite, crocoite, tellurite, witherite, and cerussite; and (iii) electro-optic materials such as potassium niobate. With materials that are significantly anisotropic, the angular regime of directions for DSW propagation turns out to be narrow. In the case of naturally occurring crystals, one has to accept the narrow angular existence domain (AED). However, exploiting the Pockels effect not only facilitates dynamic electrical control of DSW propagation, but also widens the AED for DSW propagation.

A brief survey of radiation effects on polymer dielectrics

NASA Technical Reports Server (NTRS)

Laghari, Javaid R.; Hammoud, Ahmad N.

1990-01-01

Future space power needs are extrapolated to be at least three to four orders of magnitude more than is currently available. This long-term reliable power will be required on missions such as the Space Station, Pathfinder, Space Plane, and high-powered satellites, and for defense. Electrical insulation and dielectrics are the key electrical materials needed to support these power systems, where a single-point system failure could prove catastrophic or even fatal for the whole mission. Therefore, the impact of radiation, an environmental stress, on the properties and performance of insulation and dielectrics must be understood. The influence of radiation on polymer dielectrics, the insulating materials most commonly used for power transmission and storage, is reviewed. The effects of the type of radiation, dose, rate, and total exposure on the key electrical, mechanical, and physical properties of polymer dielectrics are described and explained.

Predictive methods of some optoelectronic properties for blends based on quaternized polysulfones

NASA Astrophysics Data System (ADS)

Dobos, Adina Maria; Filimon, Anca

2017-11-01

Blends based on quaternized polysulfones were investigated in terms of optical and electronic properties. By applying the Bicerano formalism the refractive index and dielectric constant were evaluated. Also, the dielectric constant of these blends was studied as a function of temperature and frequency. As the result of the main chain structure and charged groups, an increase in theoretical values of the refractive index and dielectric constant with increasing of the ionic quaternized units content in the polymer blend occurs. Additionally, decrease in the dielectric constant with the increase of frequency and decrease of temperature was observed. Refractive index and dielectric constant values indicate that the analyzed samples are transparent and can be used in obtaining of materials with applications involving a small polarizability. Thus, the results are important in prediction of the special optoelectronic features of new polymers blends to obtain high-performance materials with applications in electronic and biomedical fields.

Fabrication of PVDF-TrFE based bilayered PbTiO3/PVDF-TrFE films capacitor

NASA Astrophysics Data System (ADS)

Nurbaya, Z.; Wahid, M. H.; Rozana, M. D.; Annuar, I.; Alrokayan, S. A. H.; Khan, H. A.; Rusop, M.

2016-07-01

Development of high performance capacitor is reaching towards new generation where the ferroelectric materials take places as the active dielectric layer. The motivation of this study is to produce high capacitance device with long life cycle. This was configured by preparing bilayered films where lead titanate as an active dielectric layer and stacked with the top dielectric layer, poly(vinyledenefluoride-trifluoroethylene). Both of them are being referred that have one in common which is ferroelectric behavior. Therefore the combination of ceramic and polymer ferroelectric material could perform optimum dielectric characteristic for capacitor applications. The fabrication was done by simple sol-gel spin coating method that being varied at spinning speed property for polymer layers, whereas maintaining the ceramic layer. The characterization of PVDF-TrFE/PbTiO3 was performed according to metal-insulator-metal stacked capacitor measurement which includes structural, dielectric, and ferroelectric measurement.

Intrinsic dielectric properties of magnetodielectric La2CoMnO6

NASA Astrophysics Data System (ADS)

Silva, R. X.; Moreira, R. L.; Almeida, R. M.; Paniago, R.; Paschoal, C. W. A.

2015-06-01

Manganite with a double perovskite structure is an attractive material because of its interesting magnetoelectric and dielectric responses. In particular, colossal dielectric constant (CDC) behavior has been observed in La2CoMnO6 (LCMO) at radio frequencies and at room temperature. In this paper, we used infrared-reflectivity spectroscopy to study a LCMO ceramic obtained through a modified Pechini's method to determine the phonon contribution to the intrinsic dielectric response of the system and to investigate the CDC origin. The analysis of the main polar modes and of the obtained phonon parameters indicate that the CDC effect of LCMO is of pure extrinsic origin. In addition, we estimated the dielectric constant and the quality factor of the material in the microwave region to be ɛ's ˜ 16 and Qu × f ˜ 124 THz, which verifies that LCMO is appropriate for application in microwave devices and circuitry.

Preparation and Electrical Properties of La0.9Sr0.1TiO3+δ

PubMed Central

Li, Wenzhi; Ma, Zhuang; Gao, Lihong; Wang, Fuchi

2015-01-01

La1−xSrxTiO3+δ (LST) has been studied in many fields, especially in the field of microelectronics due to its excellent electrical performance. Our previous theoretical simulated work has suggested that LST has good dielectric properties, but there are rare reports about this, especially experimental reports. In this paper, LST was prepared using a solid-state reaction method. The X-rays diffraction (XRD), scanning electron microscope (SEM), broadband dielectric spectroscopy, impedance spectroscopy and photoconductive measurement were used to characterize the sample. The results show that the values of dielectric parameters (the relative dielectric constant εr and dielectric loss tanδ), dependent on temperature, are stable under 350 °C and the value of the relative dielectric constant and dielectric loss are about 52–88 and 6.5 × 10−3, respectively. Its value of conductivity increases with rise in temperature, which suggests its negative temperature coefficient of the resistance. In addition, the band gap of LST is about 3.39 eV, so it belongs to a kind of wide-band-gap semiconductor materials. All these indicate that LST has anti-interference ability and good dielectric properties. It could have potential applications as an electronic material. PMID:28787995

Effect of vacuum-ultraviolet irradiation on the dielectric constant of low-k organosilicate dielectrics

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

Zheng, H.; Shohet, J. L.; Ryan, E. T.

2014-11-17

Vacuum ultraviolet (VUV) irradiation is generated during plasma processing in semiconductor fabrications, while the effect of VUV irradiation on the dielectric constant (k value) of low-k materials is still an open question. To clarify this problem, VUV photons with a range of energies were exposed on low-k organosilicate dielectrics (SiCOH) samples at room temperature. Photon energies equal to or larger than 6.0 eV were found to decrease the k value of SiCOH films. VUV photons with lower energies do not have this effect. This shows the need for thermal heating in traditional ultraviolet (UV) curing since UV light sources do notmore » have sufficient energy to change the dielectric constant of SiCOH and additional energy is required from thermal heating. In addition, 6.2 eV photon irradiation was found to be the most effective in decreasing the dielectric constant of low-k organosilicate films. Fourier Transform Infra-red Spectroscopy shows that these 6.2 eV VUV exposures removed organic porogens. This contributes to the decrease of the dielectric constant. This information provides the range of VUV photon energies that could decrease the dielectric constant of low-k materials most effectively.« less

Review on Advances of Functional Material for Additive Manufacturing

NASA Astrophysics Data System (ADS)

Zulkifli, Nur Amalina Binti; Akmal Johar, Muhammad; Faizan Marwah, Omar Mohd; Irwan Ibrahim, Mohd Halim

2017-08-01

The attempt of finding and making new materials in improving products that are already in the market are widely done by researchers nowadays. This project is focusing on making new materials for functional material through additive manufacturing application. The idea of this project came from the ability limitation of capacitor in market nowadays in storing higher charges but smaller in size. Powder glass is the new material that could to be used as a dielectric material for capacitor with the help of palm kernel oil as the binder. This paper reviews on applications done through additive manufacturing method and also types of functional materials used in this method previously. Structure of a capacitor, dielectric properties and measurement techniques that are trying to be carried out are also explains in this paper. Last part of this paper brief on the material proposal and reasons those materials are chosen. New dielectric material for capacitor which are able to store more charges but still small in size are expected to be produced as the outcome of this research.

Thin film transistors for flexible electronics: contacts, dielectrics and semiconductors.

PubMed

Quevedo-Lopez, M A; Wondmagegn, W T; Alshareef, H N; Ramirez-Bon, R; Gnade, B E

2011-06-01

The development of low temperature, thin film transistor processes that have enabled flexible displays also present opportunities for flexible electronics and flexible integrated systems. Of particular interest are possible applications in flexible sensor systems for unattended ground sensors, smart medical bandages, electronic ID tags for geo-location, conformal antennas, radiation detectors, etc. In this paper, we review the impact of gate dielectrics, contacts and semiconductor materials on thin film transistors for flexible electronics applications. We present our recent results to fully integrate hybrid complementary metal oxide semiconductors comprising inorganic and organic-based materials. In particular, we demonstrate novel gate dielectric stacks and semiconducting materials. The impact of source and drain contacts on device performance is also discussed.

Pulse Power Capability Of High Energy Density Capacitors Based on a New Dielectric Material

NASA Technical Reports Server (NTRS)

Winsor, Paul; Scholz, Tim; Hudis, Martin; Slenes, Kirk M.

1999-01-01

A new dielectric composite consisting of a polymer coated onto a high-density metallized Kraft has been developed for application in high energy density pulse power capacitors. The polymer coating is custom formulated for high dielectric constant and strength with minimum dielectric losses. The composite can be wound and processed using conventional wound film capacitor manufacturing equipment. This new system has the potential to achieve 2 to 3 J/cu cm whole capacitor energy density at voltage levels above 3.0 kV, and can maintain its mechanical properties to temperatures above 150 C. The technical and manufacturing development of the composite material and fabrication into capacitors are summarized in this paper. Energy discharge testing, including capacitance and charge-discharge efficiency at normal and elevated temperatures, as well as DC life testing were performed on capacitors manufactured using this material. TPL (Albuquerque, NM) has developed the material and Aerovox (New Bedford, MA) has used the material to build and test actual capacitors. The results of the testing will focus on pulse power applications specifically those found in electro-magnetic armor and guns, high power microwave sources and defibrillators.

Dielectric Rheo-SANS: An Instrument for the Simultaneous Interrogation of Rheology, Microstructure and Electronic Properties of Complex Fluids

NASA Astrophysics Data System (ADS)

Wagner, Norman; Richards, Jeffrey; Hipp, Julie; Butler, Paul

In situ measurements are an increasingly important tool to inform the complex relationship between nanoscale properties and macroscopic measurements. For conducting colloidal suspensions, we seek intrinsic relationships between the measured electrical and mechanical response of a material both in quiescence and under applied shear. These relationships can be used to inform the development of new materials with enhanced electrical and mechanical performance. In order to study these relationships, we have developed a dielectric rheology instrument that is compatible with small angle neutron scattering (SANS) experiments. This Dielectric RheoSANS instrument consists of a Couette geometry mounted on an ARES G2 strain controlled rheometer enclosed in a modified Forced Convection Oven (FCO). In this talk, we outline the development of the Dielectric RheoSANS instruments and demonstrate its operation using two systems - a suspension of carbon black particles in propylene carbonate and poly(3-hexylthiophene) organogel - where there is interest in how shear influences the microstructure state of the material. By monitoring the conductivity and rheological response of these materials at the same time, we can capture the entire evolution of the material response to an applied deformation. NCNR NIST Cooperative Agreement #70NANB12H239.

Dielectric Properties of Tungsten Copper Barium Ceramic as Promising Colossal-Permittivity Material

NASA Astrophysics Data System (ADS)

Wang, Juanjuan; Chao, Xiaolian; Li, Guangzhao; Feng, Lajun; Zhao, Kang; Ning, Tiantian

2017-08-01

Ba(Cu0.5W0.5)O3 (BCW) ceramic has been fabricated and its dielectric properties investigated for use in energy-storage applications, revealing a very large dielectric constant (˜104) at 1 kHz. Moreover, the colossal-permittivity BCW ceramic exhibited fine microstructure and optimal temperature stability over a wide temperature range from room temperature to 500°C. The internal barrier layer capacitor mechanism was considered to be responsible for its high dielectric properties. Based on activation values, it is concluded that doubly ionized oxygen vacancies make a substantial contribution to the conduction and relaxation behaviors at grain boundaries. This study suggests that this kind of material has potential for use in high-density energy storage applications.

Microfabricated bragg waveguide

DOEpatents

Fleming, James G.; Lin, Shawn-Yu; Hadley, G. Ronald

2004-10-19

A microfabricated Bragg waveguide of semiconductor-compatible material having a hollow core and a multilayer dielectric cladding can be fabricated by integrated circuit technologies. The microfabricated Bragg waveguide can comprise a hollow channel waveguide or a hollow fiber. The Bragg fiber can be fabricated by coating a sacrificial mandrel or mold with alternating layers of high- and low-refractive-index dielectric materials and then removing the mandrel or mold to leave a hollow tube with a multilayer dielectric cladding. The Bragg channel waveguide can be fabricated by forming a trench embedded in a substrate and coating the inner wall of the trench with a multilayer dielectric cladding. The thicknesses of the alternating layers can be selected to satisfy the condition for minimum radiation loss of the guided wave.

Investigation of dielectric properties of different cake formulations during microwave and infrared-microwave combination baking.

PubMed

Sakiyan, Ozge; Sumnu, Gulum; Sahin, Serpil; Meda, Venkatesh

2007-05-01

Dielectric properties can be used to understand the behavior of food materials during microwave processing. Dielectric properties influence the level of interaction between food and high frequency electromagnetic energy. Dielectric properties are, therefore, important in the design of foods intended for microwave preparation. In this study, it was aimed to determine the variation of dielectric properties of different cake formulations during baking in microwave and infrared-microwave combination oven. In addition, the effects of formulation and temperature on dielectric properties of cake batter were examined. Dielectric constant and loss factor of cake samples were shown to be dependent on formulation, baking time, and temperature. The increase in baking time and temperature decreased dielectric constant and loss factor of all formulations. Fat content was shown to increase dielectric constant and loss factor of cakes.

Dirac cones induced by accidental degeneracy in photonic crystals and zero-refractive-index materials.

PubMed

Huang, Xueqin; Lai, Yun; Hang, Zhi Hong; Zheng, Huihuo; Chan, C T

2011-05-29

A zero-refractive-index metamaterial is one in which waves do not experience any spatial phase change, and such a peculiar material has many interesting wave-manipulating properties. These materials can in principle be realized using man-made composites comprising metallic resonators or chiral inclusions, but metallic components have losses that compromise functionality at high frequencies. It would be highly desirable if we could achieve a zero refractive index using dielectrics alone. Here, we show that by employing accidental degeneracy, dielectric photonic crystals can be designed and fabricated that exhibit Dirac cone dispersion at the centre of the Brillouin zone at a finite frequency. In addition to many interesting properties intrinsic to a Dirac cone dispersion, we can use effective medium theory to relate the photonic crystal to a material with effectively zero permittivity and permeability. We then numerically and experimentally demonstrate in the microwave regime that such dielectric photonic crystals with reasonable dielectric constants manipulate waves as if they had near-zero refractive indices at and near the Dirac point frequency.

Enthalpy - Improved Dielectric Insulation for Superconducting Wires.

DTIC Science & Technology

1982-05-01

these materials are also bein, studickd as regenerator matrix materials for Stirling cycle cryocoolers (7), yet, 1’~l incredibly enough, their...1A0.Az 4. TI T LE (iind SThti tfe) 5 TYPE OF REPORT & PERIOD COVERFID Enthalpy - Improved Dielectric Insulation for Final JUN 80 - MAR 82...resistance, and suggestions are made for improving these conductivities. The SC-2 and SC-3 type materials have near-metallic thermal conductivities near

Dielectric waveguide gas-filled stark shift modulator

DOEpatents

Hutchinson, Donald P.; Richards, Roger K.

2003-07-22

An optical modulator includes a dielectric waveguide for receiving an optical beam and coupling energy of the optical beam into the waveguide. At least one Stark material is provided in the waveguide. A bias circuit generates a bias signal to produce an electrical field across the Stark material to shift at least one of the Stark absorption frequencies towards the frequency of the optical beam. A circuit for producing a time varying electric field across the Stark material modulates the optical beam. At least a portion of the bias field can be generated by an alternating bias signal, such as a square wave. A method of modulating optical signals includes the steps of providing a dielectric waveguide for receiving an optical beam and coupling energy of the optical beam into the waveguide, the waveguide having at least one Stark material disposed therein, and varying an electric field imposed across the Stark material.

Neural electrode resilience against dielectric damage may be improved by use of highly doped silicon as a conductive material.

PubMed

Caldwell, Ryan; Sharma, Rohit; Takmakov, Pavel; Street, Matthew G; Solzbacher, Florian; Tathireddy, Prashant; Rieth, Loren

2018-01-01

Dielectric damage occurring in vivo to neural electrodes, leading to conductive material exposure and impedance reduction over time, limits the functional lifetime and clinical viability of neuroprosthetics. We used silicon micromachined Utah Electrode Arrays (UEAs) with iridium oxide (IrO x ) tip metallization and parylene C dielectric encapsulation to understand the factors affecting device resilience and drive improvements. In vitro impedance measurements and finite element analyses were conducted to evaluate how exposed surface area of silicon and IrO x affect UEA properties. Through an aggressive in vitro reactive accelerated aging (RAA) protocol, in vivo parylene degradation was simulated on UEAs to explore agreement with our models. Electrochemical properties of silicon and other common electrode materials were compared to help inform material choice in future neural electrode designs. Exposure of silicon on UEAs was found to primarily affect impedance at frequencies >1kHz, while characteristics at 1 kHz and below were largely unchanged. Post-RAA impedance reduction of UEAs was mitigated in cases where dielectric damage was more likely to expose silicon instead of IrO x . Silicon was found to have a per-area electrochemical impedance >10×higher than many common electrode materials regardless of doping level and resistivity, making it best suited for use as a low-shunting conductor. Non-semiconductor electrode materials commonly used in neural electrode design are more susceptible to shunting neural interface signals through dielectric defects, compared to highly doped silicon. Strategic use of silicon and similar materials may increase neural electrode robustness against encapsulation failures. Copyright © 2017 Elsevier B.V. All rights reserved.

High internal free volume compositions for low-k dielectric and other applications

NASA Technical Reports Server (NTRS)

Bouffard, Jean (Inventor); Swager, Timothy M. (Inventor)

2010-01-01

The present invention provides materials, devices, and methods involving new heterocyclic, shape-persistent monomeric units with internal free volume. In some cases, materials the present invention may comprise monomers, oligomers, or polymers that incorporate a heterocyclic, shape-persistent iptycene. The present invention may provide materials having low dielectric constants and improved stability at high operating temperatures due to the electron-poor character of materials. In addition, compositions of the invention may be easily synthesized and readily modified to suit a particular application.

Solar cell contact formation using laser ablation

DOEpatents

Harley, Gabriel; Smith, David D.; Cousins, Peter John

2015-07-21

The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline material layer; and forming conductive contacts in the plurality of contact holes.

Solar cell contact formation using laser ablation

DOEpatents

Harley, Gabriel; Smith, David; Cousins, Peter

2012-12-04

The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline material layer; and forming conductive contacts in the plurality of contact holes.

Effects of Cryogenic Temperatures on Spacecraft Internal Dielectric Discharges

NASA Technical Reports Server (NTRS)

Ferguson, Dale c.; Schneider, Todd A.; Vaughn, Jason A.

2009-01-01

Abstract Most calculations of internal dielectric charging on spacecraft use tabulated values of material surface and bulk conductivities, dielectric constants, and dielectric breakdown strengths. Many of these properties are functions of temperature, and the temperature dependences are not well known. At cryogenic temperatures, where it is well known that material conductivities decrease dramatically, it is an open question as to the timescales over which buried charge will dissipate and prevent the eventual potentially disastrous discharges of dielectrics. In this paper, measurements of dielectric charging and discharging for cable insulation materials at cryogenic temperatures (approx. 90 K) are presented using a broad spectrum electron source at the NASA Marshall Space Flight Center. The measurements were performed for the James Webb Space Telescope (JWST), which will orbit at the Earth-Sun L2 point, and parts of which will be perennially at temperatures as low as 40 K. Results of these measurements seem to show that Radiation Induced Conductivity (RIC) under cryogenic conditions at L2 will not be sufficient to allow charges to bleed off of some typical cable insulation materials even over the projected JWST lifetime of a dozen years or more. After the charging and discharging measurements are presented, comparisons are made between the material conductivities that can be inferred from the measured discharges and conductivities calculated from widely used formulae. Furthermore, the measurement-inferred conductivities are compared with extrapolations of recent measurements of materials RIC and dark conductivities performed with the charge-storage method at Utah State University. Implications of the present measurements are also given for other spacecraft that may operate at cryogenic temperatures, such as probes of the outer planets or the permanently dark cratered areas on the moon. The present results will also be of interest to those who must design or operate spacecraft in more moderate cold conditions. Finally, techniques involving shielding and/or selective use of somewhat conductive insulators are presented to prevent arc-inducing charge buildup even under cryogenic conditions.

Dielectric Properties of Iron- and Sodium-Fumarate

NASA Astrophysics Data System (ADS)

Skuban, Sonja J.; Džomić, Tanja; Kapor, Agneš

2007-04-01

The behaviour of dielectric parameters such as relative dielectric constant (ɛ'), relative loss factor (V'') and ac conductivity of well known pharmaceutical materials Fe(II)-fumarate and sodium-fumarate have been studied as a function of temperature (range 303 K to 483 K) and frequency (range 0.1 Hz to 100 kHz).

Process for manufacturing multilayer capacitors

DOEpatents

Lauf, Robert J.; Holcombe, Cressie E.; Dykes, Norman L.

1996-01-01

The invention is directed to a method of manufacture of multilayer electrical components, especially capacitors, and components made by such a method. High capacitance dielectric materials and low cost metallizations layered with such dielectrics may be fabricated as multilayer electrical components by sintering the metallizations and the dielectrics during the fabrication process by application of microwave radiation.

Dielectric characterization of high-performance spaceflight materials

NASA Astrophysics Data System (ADS)

Kleppe, Nathan; Nurge, Mark A.; Bowler, Nicola

2015-03-01

As commercial space travel increases, the need for reliable structural health monitoring to predict possible weaknesses or failures of structural materials also increases. Monitoring of these materials can be done through the use of dielectric spectroscopy by comparing permittivity or conductivity measurements performed on a sample in use to that of a pristine sample from 100 μHz to 3 GHz. Fluctuations in these measured values or of the relaxation frequencies, if present, can indicate chemical or physical changes occurring within the material and the possible need for maintenance/replacement. In this work, we establish indicative trends that occur due to changes in dielectric spectra during accelerated aging of various high-performance polymeric materials: ethylene vinyl alcohol (EVOH), Poly (ether ether ketone) (PEEK), polyphenylene sulfide (PPS), and ultra-high molecular weight polyethylene (UHMWPE). Uses for these materials range from electrical insulation and protective coatings to windows and air- or space-craft parts that may be subject to environmental damage over long-term operation. Samples were prepared by thermal exposure and, separately, by ultraviolet/water-spray cyclic aging. The aged samples showed statistically-significant trends of either increasing or decreasing real or imaginary permittivity values, relaxation frequencies, conduction or the appearance of new relaxation modes. These results suggest that dielectric testing offers the possibility of nondestructive evaluation of the extent of age-related degradation in these materials.

Crosslinked polyarylene ether nitrile film as flexible dielectric materials with ultrahigh thermal stability

PubMed Central

Yang, Ruiqi; Wei, Renbo; Li, Kui; Tong, Lifen; Jia, Kun; Liu, Xiaobo

2016-01-01

Dielectric film with ultrahigh thermal stability based on crosslinked polyarylene ether nitrile is prepared and characterized. The film is obtained by solution-casting of polyarylene ether nitrile terminated phthalonitrile (PEN-Ph) combined with post self-crosslinking at high temperature. The film shows a 5% decomposition temperature over 520 °C and a glass transition temperature (Tg) around 386 °C. Stable dielectric constant and low dielectric loss are observed for this film in the frequency range of 100–200 kHz and in the temperature range of 25–300 °C. The temperature coefficient of dielectric constant is less than 0.001 °C−1 even at 400 °C. By cycling heating and cooling up to ten times or heating at 300 °C for 12 h, the film shows good reversibility and robustness of the dielectric properties. This crosslinked PEN film will be a potential candidate as high performance film capacitor electronic devices materials used at high temperature. PMID:27827436

High temperature dielectric studies of indium-substituted NiCuZn nanoferrites

NASA Astrophysics Data System (ADS)

Hashim, Mohd.; Raghasudha, M.; Shah, Jyoti; Shirsath, Sagar E.; Ravinder, D.; Kumar, Shalendra; Meena, Sher Singh; Bhatt, Pramod; Alimuddin; Kumar, Ravi; Kotnala, R. K.

2018-01-01

In this study, indium (In3+)-substituted NiCuZn nanostructured ceramic ferrites with a chemical composition of Ni0.5Cu0.25Zn0.25Fe2-xInxO4 (0.0 ≤ x ≤ 0.5) were prepared by chemical synthesis involving sol-gel chemistry. Single phased cubic spinel structure materials were prepared successfully according to X-ray diffraction and transmission electron microscopy analyses. The dielectric properties of the prepared ferrites were measured using an LCR HiTester at temperatures ranging from room temperature to 300 °C at different frequencies from 102 Hz to 5 × 106 Hz. The variations in the dielectric parameters ε‧ and (tanδ) with temperature demonstrated the frequency- and temperature-dependent characteristics due to electron hopping between the ions. The materials had low dielectric loss values in the high frequency range at all temperatures, which makes them suitable for high frequency microwave applications. A qualitative explanation is provided for the dependences of the dielectric constant and dielectric loss tangent on the frequency, temperature, and composition. Mӧssbauer spectroscopy was employed at room temperature to characterize the magnetic behavior.

Improvement of MRR and surface roughness during electrical discharge machining (EDM) using aluminum oxide powder mixed dielectric fluid

NASA Astrophysics Data System (ADS)

Khan, A. A.; Mohiuddin, A. K. M.; Latif, M. A. A.

2018-01-01

This paper discusses the effect of aluminium oxide (Al203) addition to dielectric fluid during electrical discharge machining (EDM). Aluminium oxide was added to the dielectric used in the EDM process to improve its performance when machining the stainless steel AISI 304, while copper was used as the electrode. Effect of the concentration of Al203 (0.3 mg/L) in dielectric fluid was compared with EDM without any addition of Al203. Surface quality of stainless steel and the material removal rate were investigated. Design of the experiment (DOE) was used for the experimental plan. Statistical analysis was done using ANOVA and then appropriate model was designated. The experimental results show that with dispersing of aluminium oxide in dielectric fluid surface roughness was improved while the material removal rate (MRR) was increased to some extent. These indicate the improvement of EDM performance using aluminium oxide in dielectric fluid. It was also found that with increase in pulse on time both MRR and surface roughness increase sharply.

Nonlinear dielectric thin films for high-power electric storage with energy density comparable with electrochemical supercapacitors.

PubMed

Yao, Kui; Chen, Shuting; Rahimabady, Mojtaba; Mirshekarloo, Meysam Sharifzadeh; Yu, Shuhui; Tay, Francis Eng Hock; Sritharan, Thirumany; Lu, Li

2011-09-01

Although batteries possess high energy storage density, their output power is limited by the slow movement of charge carriers, and thus capacitors are often required to deliver high power output. Dielectric capacitors have high power density with fast discharge rate, but their energy density is typically much lower than electrochemical supercapacitors. Increasing the energy density of dielectric materials is highly desired to extend their applications in many emerging power system applications. In this paper, we review the mechanisms and major characteristics of electric energy storage with electrochemical supercapacitors and dielectric capacitors. Three types of in-house-produced ferroic nonlinear dielectric thin film materials with high energy density are described, including (Pb(0.97)La(0.02))(Zr(0.90)Sn(0.05)Ti(0.05))O(3) (PLZST) antiferroelectric ceramic thin films, Pb(Zn(1/3)Nb(2/3))O(3-)Pb(Mg(1/3)Nb(2/3))O(3-)PbTiO(3) (PZN-PMN-PT) relaxor ferroelectric ceramic thin films, and poly(vinylidene fluoride) (PVDF)-based polymer blend thin films. The results showed that these thin film materials are promising for electric storage with outstandingly high power density and fairly high energy density, comparable with electrochemical supercapacitors.

Dielectric and magnetic studies of BaTi0.5Fe0.5O3 ceramic materials, synthesized by solid state sintering.

PubMed

Samuvel, K; Ramachandran, K

2015-02-05

A comparative study of the surface morphology, dielectric and magnetic properties of the BaTi0.5Fe0.5O3 (BTFO) ceramics materials. This has been carried out by synthesizing the samples in different routes. BTFO samples have shown single phased 12R type hexagonal structure with R3m, P4mm space group. Interfacial effects on the dielectric properties of the samples have been understood by Cole-Cole plots in complex impedance and modulus formalism. It has been identified that huge dielectric constant (10(3)-10(6)) at lower frequencies is largely contributed by the heterogeneous electronic microstructure at the interfaces of grains. Modulus formalism has identified the effects of both grain and grain boundary microstructure on the dielectric properties, particularly in chemical routed samples. The order of grain boundary resistivity suggests the semiconductor/insulator class of the material. The grain boundary resistivity of the mechanical alloyed samples is remarkably lower than the solid state and chemical routed samples. Few samples have of the samples have exhibited signature of ferromagnetism at the room temperature. Copyright © 2014 Elsevier B.V. All rights reserved.

Enhanced dielectric response of GeO{sub 2}-doped CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics

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

Amaral, F.; School of Technology and Management of Oliveira do Hospital, Oliveira do Hospital, 3400-124 Oliveira; Rubinger, C. P. L.

2009-02-01

CaCu{sub 3}Ti{sub 4}O{sub 12} ceramic samples were prepared by solid state conventional route using stoichiometric amounts of CuO, TiO{sub 2}, and CaCO{sub 3}. Afterward the material was doped with GeO{sub 2} with concentrations up to 6% by weight and sintered at 1050 deg. C for 12 h. The influence of doping on the microstructure, vibrational modes, and dielectric properties of the material was investigated by x-ray diffraction, scanning electron microscopy coupled with an energy dispersive spectrometer, and infrared and dielectric measurements between 100 Hz and 30 MHz. The materials presented huge dielectric response, which increases with doping level relative tomore » undoped CaCu{sub 3}Ti{sub 4}O{sub 12}. The main effect of doping on the microstructure is the segregation of Cu-rich phase in the ceramic grain boundaries. Cole-Cole modeling correlates well the effects of this segregation with the relaxation parameters obtained. The intrinsic phonon contributions for the dielectric response were obtained and discussed together with the structural evolution of the system.« less

Dielectric properties of polyhedral oligomeric silsesquioxane (POSS)-based nanocomposites at 77k

NASA Astrophysics Data System (ADS)

Pan, Ming-Jen; Gorzkowski, Edward; McAllister, Kelly

2011-10-01

The goal of this study is to develop dielectric nanocomposites for high energy density applications at liquid nitrogen temperature by utilizing a unique nano-material polyhedral oligomeric silsesquioxanes (POSS). A POSS molecule is consisted of a silica cage core with 8 silicon and 12 oxygen atoms and organic functional groups attached to the corners of the cage. In this study, we utilize POSS for the fabrication of nanocomposites both as a silica nanoparticle filler to enhance the breakdown strength and as a surfactant for effective dispersion of high permittivity ceramic nanoparticles in a polymer matrix. The matrix materials selected for the study are polyvinylidene fluoride (PVDF) and poly(methyl methacrylate) (PMMA). The ceramic nanoparticles are barium strontium titanate (BST 50/50) and strontium titanate. The dielectric properties of the solution-cast nanocomposites films were correlated to the composition and processing conditions. We determined that the addition of POSS did not provide enhanced dielectric performance in PVDF- and PMMA-based materials at either room temperature or 77K. In addition, we found that the dielectric breakdown strength of PMMA is lower at 77K than at room temperature, contradicting literature data.

Analysis of transmittance properties in 1D hybrid dielectric photonic crystal containing superconducting thin films

NASA Astrophysics Data System (ADS)

Soltani, Osswa; Zaghdoudi, Jihene; Kanzari, Mounir

2018-06-01

By means of two fluid model and transfer matrix method (TMM), we investigate theoretically the transmittance properties of a defective hybrid dielectric-dielectric photonic crystal that contains a superconducting material as a defect layer. The considered hybrid photonic structure is: H(LH) 7(HLSLH) P H(LH) 7 , where H is the high refractive index dielectric, L is the low refractive index dielectric, S is the superconducting material and P is the repetitive number. The results show that the variation of the number and the positions of the transmissions modes depend strongly on the repetitive number P, the temperature T and the thickness of the layer S. An improvement of the spectral response is obtained with the exponential gradation of layer thicknesses dj =d0 + βejα , where d0 is the initial thickness of the layer j, α and β are two particular constants for each material. In addition, the effect of the incident angle for both transverse electric (TE) and transverse magnetic (TM) polarizations on the transmittance spectrum is discussed. As a result, we propose a tunable narrow stop-band polychromatic filter that covers the visible wavelength.

Time Dependent Dielectric Breakdown in Copper Low-k Interconnects: Mechanisms and Reliability Models

PubMed Central

Wong, Terence K.S.

2012-01-01

The time dependent dielectric breakdown phenomenon in copper low-k damascene interconnects for ultra large-scale integration is reviewed. The loss of insulation between neighboring interconnects represents an emerging back end-of-the-line reliability issue that is not fully understood. After describing the main dielectric leakage mechanisms in low-k materials (Poole-Frenkel and Schottky emission), the major dielectric reliability models that had appeared in the literature are discussed, namely: the Lloyd model, 1/E model, thermochemical E model, E1/2 models, E2 model and the Haase model. These models can be broadly categorized into those that consider only intrinsic breakdown (Lloyd, 1/E, E and Haase) and those that take into account copper migration in low-k materials (E1/2, E2). For each model, the physical assumptions and the proposed breakdown mechanism will be discussed, together with the quantitative relationship predicting the time to breakdown and supporting experimental data. Experimental attempts on validation of dielectric reliability models using data obtained from low field stressing are briefly discussed. The phenomenon of soft breakdown, which often precedes hard breakdown in porous ultra low-k materials, is highlighted for future research.

Impact of device engineering on analog/RF performances of tunnel field effect transistors

NASA Astrophysics Data System (ADS)

Vijayvargiya, V.; Reniwal, B. S.; Singh, P.; Vishvakarma, S. K.

2017-06-01

The tunnel field effect transistor (TFET) and its analog/RF performance is being aggressively studied at device architecture level for low power SoC design. Therefore, in this paper we have investigated the influence of the gate-drain underlap (UL) and different dielectric materials for the spacer and gate oxide on DG-TFET (double gate TFET) and its analog/RF performance for low power applications. Here, it is found that the drive current behavior in DG-TFET with a UL feature while implementing dielectric material for the spacer is different in comparison to that of DG-FET. Further, hetero gate dielectric-based DG-TFET (HGDG-TFET) is more resistive against drain-induced barrier lowering (DIBL) as compared to DG-TFET with high-k (HK) gate dielectric. Along with that, as compared to DG-FET, this paper also analyses the attributes of UL and dielectric material on analog/RF performance of DG-TFET in terms of transconductance (gm ), transconductance generation factor (TGF), capacitance, intrinsic resistance (Rdcr), cut-off frequency (F T), and maximum oscillation frequency (F max). The LK spacer-based HGDG-TFET with a gate-drain UL has the potential to improve the RF performance of device.

Three-phase Fe3O4/MWNT/PVDF nanocomposites with high dielectric constant for embedded capacitor

NASA Astrophysics Data System (ADS)

Wang, Haiyun; Fu, Qiong; Luo, Jiangqi; Zhao, Dongmei; Luo, Laihui; Li, Weiping

2017-06-01

To get the dielectric material with a high dielectric constant and low dielectric loss, the modified multiwalled carbon nanotube (MWNT-S) and ferroferric oxide (Fe3O4) particles were embedded into polyvinylidene fluoride (PVDF) to fabricate the Fe3O4/MWNT-S/PVDF ternary composites. The maximum dielectric constant of these composites can be up to 3490 at a very low filler fraction, and dielectric loss can be suppressed below 0.5. The small amount of the second filler (Fe3O4) can accelerate the formation of a percolation conductive network and improve the interfacial polarization. Therefore, the excellent dielectric properties can be achieved at low loading of fillers.

The study of electrical conduction mechanisms. [dielectric response of lunar fines

NASA Technical Reports Server (NTRS)

Morrison, H. F.

1974-01-01

The dielectric response of lunar fines 74241,2 is presented in the audio-frequency range and under lunarlike conditions. Results suggest that volatiles are released during storage and transport of the lunar sample. Apparently, subsequent absorption of volatiles on the sample surface alter its dielectric response. The assumed volatile influence disappear after evacuation. A comparison of the dielectric properties of lunar and terrestrial materials as a function of density, temperature, and frequency indicates that if the lunar simulator analyzed were completely devoid of atmospheric moisture it would present dielectric losses smaller than those of the lunar sample. It is concluded that density prevails over temperature as the controlling factor of dielectric permittivity in the lunar regolith and that dielectric losses vary slowly with depth.

Self assembled monolayers of octadecyltrichlorosilane for dielectric materials

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

Kumar, Vijay, E-mail: cirivijaypilani@gmail.com; Mechanical Engineering Department, Birla Institute of Technology and Science-Pilani; Puri, Paridhi

2016-04-13

Treatment of surfaces to change the interaction of fluids with them is a critical step in constructing useful microfluidics devices, especially those used in biological applications. Selective modification of inorganic materials such as Si, SiO{sub 2} and Si{sub 3}N{sub 4} is of great interest in research and technology. We evaluated the chemical formation of OTS self-assembled monolayers on silicon substrates with different dielectric materials. Our investigations were focused on surface modification of formerly used common dielectric materials SiO{sub 2}, Si{sub 3}N{sub 4} and a-poly. The improvement of wetting behaviour and quality of monolayer films were characterized using Atomic force microscope,more » Scanning electron microscope, Contact angle goniometer, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) monolayer deposited oxide surface.« less

PREFACE: Dielectrics 2009: Measurement Analysis and Applications

NASA Astrophysics Data System (ADS)

Vaughan, Alun; Williams, Graham

2009-07-01

The conference Dielectrics 2009: Measurements, Analysis and Applications represents a significant milestone in the evolution of dielectrics research in the UK. It is reasonable to state that the academic study of dielectrics has led to many fundamental advances and that dielectric materials underpin the modern world in devices ranging from field effect transistors, which operate at extremely high fields, albeit low voltages, to the high voltage plants that provide the energy that powers our economy. The origins of the Dielectrics Group of the Institute of Physics (IOP), which organized this conference, can be traced directly back to the early 1960s, when Professor Mansel Davies was conducting research into the dielectric relaxation behaviour of polar liquids and solids at The Edward Davies Chemical Laboratories of the University College of Wales, Aberystwyth. He was already well-known internationally for his studies of molecular structure and bonding of small molecules, using infra-red-spectroscopy, and of the physical properties of hydrogen-bonded liquids and solids, using thermodynamic methods. Dielectric spectroscopy was a fairly new area for him and he realized that opportunities for scientists in the UK to gather together and discuss their research in this developing area of physical chemistry/chemical physics were very limited. He conceived the idea of forming a Dielectrics Discussion Group (DDG), which would act as a meeting point and provide a platform for dielectrics research in the UK and beyond and, as a result, a two-day Meeting was convened in the spring of 1968 at Gregynog Hall of the University of Wales, near Newtown, Montgomeryshire. It was organized by Mansel Davies, Alun Price and Graham Williams, all physical chemists from the UCW, Aberystwyth. Fifty scientists attended, being a mix of physical chemists, theoretical chemists, physicists, electrical engineers, polymer and materials scientists, all from the UK, except Dr Brendan Scaife of Trinity 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 2001 the Annual Meetings focused on numerous topics, including relaxation and conduction processes in liquids, solids, liquid crystals, synthetic polymers and biopolymers, piezoelectric materials, electrets and ferroelectrets, interfacial phenomena, high field conduction and breakdown phenomena in solids, liquids and gases and, importantly, the remarkable developments in dielectric instrumentation during this period. These activities reflected the need, and willingness, to move dielectrics researches with the times. As examples of the variety and diversity of these meetings we may refer briefly to the 1981, 1989 and 1996 Meetings. The 1981 Oxford Meeting on High Field Phenomena in Dielectrics included strong themes on fundamental and practical effects of high E-fields on the dielectric and conduction behaviour of liquids and solids, electrical treeing and dielectric breakdown, non-linear dielectric effects, electrets, thin-film devices and electro-rheology. The late 1980's had seen large initiatives in the UK and globally in the general area of Molecular Electronics so, in timely fashion, this was the subject of the 1989 Meeting in Bangor. The 1996 Smart Dielectrics Meeting at Canterbury reported subsequent advances in designer materials having electro-responsive and electro-optical properties. The programme concerned electro- and photo-active materials, mainly organic, in the form of polar dielectrics, polyelectrolytes, organic semi- and photo-conductors, photo-refractive polymer films, organic ferroelectric films, liquid crystalline polymer films, piezo- and pyro-electric polymer films, electroluminescent polymers, electro-rheological fluids and non-linear optical polymer films as described by leading international scientists. The physico-chemical functions of the materials were demonstrated and interpreted in terms of fundamental molecular properties. An Archive, containing full details of all the Meetings of the DDG and the Dielectrics Society, has been placed on the Website of the IOP Dielectrics Group by Professor John Fothergill. The 2009 meeting of The Dielectrics Group of the IOP at Reading was therefore held to celebrate 40 years of coordinated dielectrics research activity in the UK and beyond, as presented at these DDG and Dielectrics Society Meetings. To reflect the range of topics addressed since the first DDG meeting in 1968, the organizing committee chose to break away from the tradition of a strongly- themed event and, rather, adopted a general, inclusive approach, albeit based upon four broad technical areas: Theme 1: Molecular and bulk relaxation processes Theme 2: Space charge and charge transport in insulators Theme 3: Functional materials Theme 4: Bio-dielectrics and complex systems. The result was a highly successful conference that attracted some 90 delegates from 11 countries, giving the event a truly international flavour, and which included both regular and new attendees. Consequently, the organizing committee would like to thank, our colleagues at the IOP, the invited speakers, our sponsors at National Grid, EDF Energy and Dow Wire and Cables and all the delegates for making the event such a success. Professor Alun Vaughan, Professor Graham Williams

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

NASA Astrophysics Data System (ADS)

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.

Structural, morphological, dielectric and impedance spectroscopy of lead-free Bi(Zn2/3Ta1/3)O3 electronic material

NASA Astrophysics Data System (ADS)

Halder, S.; Bhuyan, S.; Das, S. N.; Sahoo, S.; Choudhary, R. N. P.; Das, P.; Parida, K.

2017-12-01

A lead-free dielectric material [Bi(Zn2/3Ta1/3)O3] has been prepared using a solid state reaction technique at high-temperature. The resistive, conducting and capacitive characteristics of the prepared electronic material have been studied in different experimental conditions. The determination of basic crystal parameters and reflection indices confirm the development of polycrystalline compound with orthorhombic crystal structure. The study of frequency-temperature dependence of ac conductivity illustrates the nature and conduction mechanism of the material. On the basis of observed impedance data and detailed dielectric analysis, the existence of non-Debye type relaxation has been affirmed. The electronic charge carriers of compound have short range order that has been validated from the complex modulus and impedance spectrum. The detailed studies of resistive, capacitive, microstructural characteristics of the prepared material provide some useful data for considering the material as an electronic component for fabrication of devices.

Medium band gap polymer based solution-processed high-κ composite gate dielectrics for ambipolar OFET

NASA Astrophysics Data System (ADS)

Canımkurbey, Betül; Unay, Hande; Çakırlar, Çiğdem; Büyükköse, Serkan; Çırpan, Ali; Berber, Savas; Altürk Parlak, Elif

2018-03-01

The authors present a novel ambipolar organic filed-effect transistors (OFETs) composed of a hybrid dielectric thin film of Ta2O5:PMMA nanocomposite material, and solution processed poly(selenophene, benzotriazole and dialkoxy substituted [1,2-b:4, 5-b‧] dithiophene (P-SBTBDT)-based organic semiconducting material as the active layer of the device. We find that the Ta2O5:PMMA insulator shows n-type conduction character, and its combination with the p-type P-SBTBDT organic semiconductor leads to an ambipolar OFET device. Top-gated OFETs were fabricated on glass substrate consisting of interdigitated ITO electrodes. P-SBTBDT-based material was spin coated on the interdigitated ITO electrodes. Subsequently, a solution processed Ta2O5:PMMA nanocomposite material was spin coated, thereby creating the gate dielectric layer. Finally, as a gate metal, an aluminum layer was deposited by thermal evaporation. The fabricated OFETs exhibited an ambipolar performance with good air-stability, high field-induced current and relatively high electron and hole mobilities although Ta2O5:PMMA nanocomposite films have slightly higher leakage current compared to the pure Ta2O5 films. Dielectric properties of the devices with different ratios of Ta2O5:PMMA were also investigated. The dielectric constant varied between 3.6 and 5.3 at 100 Hz, depending on the Ta2O5:PMMA ratio.

Development of Dielectric Elastomer Nanocomposites as Stretchable and Flexible Actuating Materials

NASA Astrophysics Data System (ADS)

Wang, Yu

Dielectric elastomers (DEs) are a new type of smart materials showing promising functionalities as energy harvesting materials as well as actuating materials for potential applications such as artificial muscles, implanted medical devices, robotics, loud speakers, micro-electro-mechanical systems (MEMS), tunable optics, transducers, sensors, and even generators due to their high electromechanical efficiency, stability, lightweight, low cost, and easy processing. Despite the advantages of DEs, technical challenges must be resolved for wider applications. A high electric field of at least 10-30 V/um is required for the actuation of DEs, which limits the practical applications especially in biomedical fields. We tackle this problem by introducing the multiwalled carbon nanotubes (MWNTs) in DEs to enhance their relative permittivity and to generate their high electromechanical responses with lower applied field level. This work presents the dielectric, mechanical and electromechanical properties of DEs filled with MWNTs. The micromechanics-based finite element models are employed to describe the dielectric, and mechanical behavior of the MWNT-filled DE nanocomposites. A sufficient number of models are computed to reach the acceptable prediction of the dielectric and mechanical responses. In addition, experimental results are analyzed along with simulation results. Finally, laser Doppler vibrometer is utilized to directly detect the enhancement of the actuation strains of DE nanocomposites filled with MWNTs. All the results demonstrate the effective improvement in the electromechanical properties of DE nanocomposites filled with MWNTs under the applied electric fields.

Synthesized tissue-equivalent dielectric phantoms using salt and polyvinylpyrrolidone solutions.

PubMed

Ianniello, Carlotta; de Zwart, Jacco A; Duan, Qi; Deniz, Cem M; Alon, Leeor; Lee, Jae-Seung; Lattanzi, Riccardo; Brown, Ryan

2018-07-01

To explore the use of polyvinylpyrrolidone (PVP) for simulated materials with tissue-equivalent dielectric properties. PVP and salt were used to control, respectively, relative permittivity and electrical conductivity in a collection of 63 samples with a range of solute concentrations. Their dielectric properties were measured with a commercial probe and fitted to a 3D polynomial in order to establish an empirical recipe. The material's thermal properties and MR spectra were measured. The empirical polynomial recipe (available at https://www.amri.ninds.nih.gov/cgi-bin/phantomrecipe) provides the PVP and salt concentrations required for dielectric materials with permittivity and electrical conductivity values between approximately 45 and 78, and 0.1 to 2 siemens per meter, respectively, from 50 MHz to 4.5 GHz. The second- (solute concentrations) and seventh- (frequency) order polynomial recipe provided less than 2.5% relative error between the measured and target properties. PVP side peaks in the spectra were minor and unaffected by temperature changes. PVP-based phantoms are easy to prepare and nontoxic, and their semitransparency makes air bubbles easy to identify. The polymer can be used to create simulated material with a range of dielectric properties, negligible spectral side peaks, and long T 2 relaxation time, which are favorable in many MR applications. Magn Reson Med 80:413-419, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Handbook of the optical, thermal and mechanical properties of six polycrystalline dielectric materials

NASA Technical Reports Server (NTRS)

Dewitt, D. P.

1972-01-01

The design data for six polycrystalline dielectric materials are presented to describe the optical, thermal, and mechanical properties. The materials are aluminum oxide, calcium fluoride, magnesium fluoride, magnesium oxide, silicon dioxide, and titanium dioxide. The primary interest is in the polycrystalline state, although single crystal data are included when appropriate. The temperature range is room temperature to melting point. The wavelength range is from near ultraviolet to near infrared.

Electrostatic Discharge Properties of Irradiated Nanocomposites

DTIC Science & Technology

2009-03-01

47 24. Example Plot of Mean Current vs . Voltage Difference Curves ..................................48 25...across dielectric surfaces and prevent ESD arcing to very high voltage differentials (Figure 2) [7]. All of these drastic alterations in material...structure currents (3) Area thickness and dielectric strength of the material (4) Total charge involved in the event (5) Breakdown voltage (6) Current

Integral Equation Method for Electromagnetic Wave Propagation in Stratified Anisotropic Dielectric-Magnetic Materials

NASA Astrophysics Data System (ADS)

Shu, Wei-Xing; Fu, Na; Lü, Xiao-Fang; Luo, Hai-Lu; Wen, Shuang-Chun; Fan, Dian-Yuan

2010-11-01

We investigate the propagation of electromagnetic waves in stratified anisotropic dielectric-magnetic materials using the integral equation method (IEM). Based on the superposition principle, we use Hertz vector formulations of radiated fields to study the interaction of wave with matter. We derive in a new way the dispersion relation, Snell's law and reflection/transmission coefficients by self-consistent analyses. Moreover, we find two new forms of the generalized extinction theorem. Applying the IEM, we investigate the wave propagation through a slab and disclose the underlying physics, which are further verified by numerical simulations. The results lead to a unified framework of the IEM for the propagation of wave incident either from a medium or vacuum in stratified dielectric-magnetic materials.

Cavity resonator for dielectric measurements of high-ɛ, low loss materials, demonstrated with barium strontium zirconium titanate ceramics

NASA Astrophysics Data System (ADS)

Marksteiner, Quinn R.; Treiman, Michael B.; Chen, Ching-Fong; Haynes, William B.; Reiten, M. T.; Dalmas, Dale; Pulliam, Elias

2017-06-01

A resonant cavity method is presented which can measure loss tangents and dielectric constants for materials with dielectric constant from 150 to 10 000 and above. This practical and accurate technique is demonstrated by measuring barium strontium zirconium titanate bulk ferroelectric ceramic blocks. Above the Curie temperature, in the paraelectric state, barium strontium zirconium titanate has a sufficiently low loss that a series of resonant modes are supported in the cavity. At each mode frequency, the dielectric constant and loss tangent are obtained. The results are consistent with low frequency measurements and computer simulations. A quick method of analyzing the raw data using the 2D static electromagnetic modeling code SuperFish and an estimate of uncertainties are presented.

Rotating cylindrical and spherical triboelectric generators

DOEpatents

Wang, Zhong Lin; Zhu, Guang; Yang, Ya; Zhang, Hulin; Hu, Youfan; Yang, Jin; Jing, Qingshen

2017-02-14

A generator includes a first member, a second member and a sliding mechanism. The first member includes a first electrode and a first dielectric layer affixed to the first electrode. The first dielectric layer includes a first material that has a first rating on a triboelectric series. The second member includes a second material that has a second rating on the triboelectric series that is different from the first rating. The second member includes a second electrode. The second member is disposed adjacent to the first dielectric layer so that the first dielectric layer is disposed between the first electrode and the second electrode. The sliding mechanism is configured to cause relative movement between the first member and the second member, thereby generating an electric potential imbalance between the first electrode and the second electrode.

Cylindrical and spherical triboelectric generators

DOEpatents

Wang, Zhong Lin; Zhu, Guang; Yang, Ya; Zhang, Hulin; Hu, Youfan; Yang, Jin; Jing, Qingshen; Bai, Peng

2017-12-12

A generator includes a first member, a second member and a sliding mechanism. The first member includes a first electrode and a first dielectric layer affixed to the first electrode. The first dielectric layer includes a first material that has a first rating on a triboelectric series. The second member includes a second material that has a second rating on the triboelectric series that is different from the first rating. The second member includes a second electrode. The second member is disposed adjacent to the first dielectric layer so that the first dielectric layer is disposed between the first electrode and the second electrode. The sliding mechanism is configured to cause relative movement between the first member and the second member, thereby generating an electric potential imbalance between the first electrode and the second electrode.

Colossal dielectric behavior of semiconducting Sr2TiMnO6 ceramics

NASA Astrophysics Data System (ADS)

Meher, K. R. S. Preethi; Varma, K. B. R.

2009-02-01

Manganitelike double perovskite Sr2TiMnO6 (STMO) ceramics fabricated from the powders synthesized via the solid-state reaction route, exhibited dielectric constants as high as ˜105 in the low frequency range (100 Hz-10 kHz) at room temperature. The Maxwell-Wagner type of relaxation mechanism was found to be more appropriate to rationalize such high dielectric constant values akin to that observed in materials such as KxTiyNi(1-x-y)O and CaCu3Ti4O12. The dielectric measurements carried out on the samples with different thicknesses and electrode materials reflected the influence of extrinsic effects. The impedance studies (100 Hz-10 MHz) in the 180-300 K temperature range revealed the presence of two dielectric relaxations corresponding to the grain boundary and the electrode. The dielectric response of the grain boundary was found to be weakly dependent on the dc bias field (up to 11 V/cm). However, owing to the electrode polarization, the applied ac/dc field had significant effect on the low frequency dielectric response. At low temperatures (100-180 K), the dc conductivity of STMO followed a variable range hopping behavior. Above 180 K, it followed the Arrhenius behavior because of the thermally activated conduction process. The bulk conductivity relaxation owing to the localized hopping of charge carriers obeyed the typical universal dielectric response.

Multilayer dielectric diffraction gratings

DOEpatents

Perry, Michael D.; Britten, Jerald A.; Nguyen, Hoang T.; Boyd, Robert; Shore, Bruce W.

1999-01-01

The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described.

Multilayer dielectric diffraction gratings

DOEpatents

Perry, M.D.; Britten, J.A.; Nguyen, H.T.; Boyd, R.; Shore, B.W.

1999-05-25

The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described. 7 figs.

Low-Dielectric Polyimides

NASA Technical Reports Server (NTRS)

St. Clair, Anne K.; St. Clair, Terry L.; Winfree, William P.; Emerson, Bert R., Jr.

1989-01-01

New process developed to produce aromatic condensation polyimide films and coatings having dielectric constants in range of 2.4 to 3.2. Materials better electrical insulators than state-of-the-art commercial polyimides. Several low-dielectric-constant polyimides have excellent resistance to moisture. Useful as film and coating materials for both industrial and aerospace applications where high electrical insulation, resistance to moisture, mechanical strength, and thermal stability required. Applicable to production of high-temperature and moisture-resistance adhesives, films, photoresists, and coatings. Electronic applications include printed-circuit boards, both of composite and flexible-film types and potential use in automotive, aerospace, and electronic industries.

Process for manufacturing multilayer capacitors

DOEpatents

Lauf, R.J.; Holcombe, C.E.; Dykes, N.L.

1996-01-02

The invention is directed to a method of manufacture of multilayer electrical components, especially capacitors, and components made by such a method. High capacitance dielectric materials and low cost metallizations layered with such dielectrics may be fabricated as multilayer electrical components by sintering the metallizations and the dielectrics during the fabrication process by application of microwave radiation. 4 figs.

Nonexistence of Smooth Electromagnetic Fields in Nonlinear Dielectrics. II. Shock Development in a Half-Space.

DTIC Science & Technology

1982-03-01

NUMB9ER 00 AU THOR(s) 8. CON7RACT OR GRANT .%Uv3ERHj) Frederick Bloom AFOSR-81-0171 PERFORMING ORGANIZATION NAME AND ADDRESS 10. PrOGRAK ELEMAE:NT...material coff -iceret which may be associated with a particular nonlinear dielectric substance. For most common nonlinear dielectric substance, e

Thin-Ribbon Tapered Couplers For Dielectric Waveguides

NASA Technical Reports Server (NTRS)

Otoshi, Tom Y.; Shimabukuro, Fred I.; Yeh, Cavour

1996-01-01

Thin-ribbon tapered couplers proposed for launching electro-magnetic waves into dielectric waveguides, which include optical fibers. Intended for use with ribbon dielectric waveguides designed for operation at millimeter or submillimeter wavelengths, made of high-relative-permittivity, low-loss materials and thicknesses comparable to or less than free-space design wavelengths. Coupling efficiencies exceeds those of older tapered couplers.

Fruit and Vegetable Quality Assessment via Dielectric Sensing

PubMed Central

El Khaled, Dalia; Novas, Nuria; Gazquez, Jose A.; Garcia, Rosa M.; Manzano-Agugliaro, Francisco

2015-01-01

The demand for improved food quality has been accompanied by a technological boost. This fact enhances the possibility of improving the quality of horticultural products, leading towards healthier consumption of fruits and vegetables. A better electrical characterization of the dielectric properties of fruits and vegetables is required for this purpose. Moreover, a focused study of dielectric spectroscopy and advanced dielectric sensing is a highly interesting topic. This review explains the dielectric property basics and classifies the dielectric spectroscopy measurement techniques. It comprehensively and chronologically covers the dielectric experiments explored for fruits and vegetables, along with their appropriate sensing instrumentation, analytical modelling methods and conclusions. An in-depth definition of dielectric spectroscopy and its usefulness in the electric characterization of food materials is presented, along with the various sensor techniques used for dielectric measurements. The collective data are tabulated in a summary of the dielectric findings in horticultural field investigations, which will facilitate more advanced and focused explorations in the future. PMID:26131680

Inductive dielectric analyzer

NASA Astrophysics Data System (ADS)

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

2017-03-01

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.

Effect of surface moisture on dielectric behavior of ultrafine BaTiO3 particulates.

NASA Technical Reports Server (NTRS)

Mountvala, A. J.

1971-01-01

The effects of adsorbed H2O on the dielectric properties of ultrafine BaTiO3 particulates of varying particle size and environmental history were determined. The dielectric behavior depends strongly on surface hydration. No particle size dependence of dielectric constant was found for dehydroxylated surfaces in ultrafine particulate (unsintered) BaTiO3 materials. For equivalent particle sizes, the ac conductivity is sensitive to surface morphology. Reactions with H2O vapor appear to account for the variations in dielectric properties. Surface dehydration was effectively accomplished by washing as-received powders in isopropanol.

Growth, strain relaxation properties and high-κ dielectric integration of mixed-anion GaAs{sub 1-y}Sb{sub y} metamorphic materials

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

Zhu, Y.; Clavel, M.; Goley, P.

Mixed-anion, GaAs{sub 1-y}Sb{sub y} metamorphic materials with a wide range of antimony (Sb) compositions extending from 15% to 62%, were grown by solid source molecular beam epitaxy (MBE) on GaAs substrates. The impact of different growth parameters on the Sb composition in GaAs{sub 1-y}Sb{sub y} materials was systemically investigated. The Sb composition was well-controlled by carefully optimizing the As/Ga ratio, the Sb/Ga ratio, and the substrate temperature during the MBE growth process. High-resolution x-ray diffraction demonstrated a quasi-complete strain relaxation within each composition of GaAs{sub 1-y}Sb{sub y}. Atomic force microscopy exhibited smooth surface morphologies across the wide range of Sbmore » compositions in the GaAs{sub 1-y}Sb{sub y} structures. Selected high-κ dielectric materials, Al{sub 2}O{sub 3}, HfO{sub 2}, and Ta{sub 2}O{sub 5} were deposited using atomic layer deposition on the GaAs{sub 0.38}Sb{sub 0.62} material, and their respective band alignment properties were investigated by x-ray photoelectron spectroscopy (XPS). Detailed XPS analysis revealed a valence band offset of >2 eV for all three dielectric materials on GaAs{sub 0.38}Sb{sub 0.62}, indicating the potential of utilizing these dielectrics on GaAs{sub 0.38}Sb{sub 0.62} for p-type metal-oxide-semiconductor (MOS) applications. Moreover, both Al{sub 2}O{sub 3} and HfO{sub 2} showed a conduction band offset of >2 eV on GaAs{sub 0.38}Sb{sub 0.62}, suggesting these two dielectrics can also be used for n-type MOS applications. The well-controlled Sb composition in several GaAs{sub 1-y}Sb{sub y} material systems and the detailed band alignment analysis of multiple high-κ dielectric materials on a fixed Sb composition, GaAs{sub 0.38}Sb{sub 0.62}, provides a pathway to utilize GaAs{sub 1-y}Sb{sub y} materials in future microelectronic and optoelectronic applications.« less

Strong Photoluminescence Enhancement in All-Dielectric Fano Metasurface with High Quality Factor.

PubMed

Yuan, Shuai; Qiu, Xingzhi; Cui, Chengcong; Zhu, Liangqiu; Wang, Yuxi; Li, Yi; Song, Jinwen; Huang, Qingzhong; Xia, Jinsong

2017-11-28

All-dielectric metamaterials offer great flexibility for controlling light-matter interaction, owing to their strong electric and magnetic resonances with negligible loss at wavelengths above the material bandgap. Here, we propose an all-dielectric asymmetric metasurface structure exhibiting high quality factor and prominent Fano line shape. Over three-orders photoluminescence enhancement is demonstrated in the fabricated all-dielectric metasurface with record-high quality factor of 1011. We find this strong emission enhancement is attributed to the coherent Fano resonances, which originate from the destructive interferences of antisymmetric displacement currents in the asymmetric all-dielectric metasurface. Our observations show a promising approach to realize light emitters based on all-dielectric metasurfaces.

Dielectric breakdown of additively manufactured polymeric materials

DOE PAGES

Monzel, W. Jacob; Hoff, Brad W.; Maestas, Sabrina S.; ...

2016-01-11

Dielectric strength testing of selected Polyjet-printed polymer plastics was performed in accordance with ASTM D149. This dielectric strength data is compared to manufacturer-provided dielectric strength data for selected plastics printed using the stereolithography (SLA), fused deposition modeling (FDM), and selective laser sintering (SLS) methods. Tested Polyjet samples demonstrated dielectric strengths as high as 47.5 kV/mm for a 0.5 mm thick sample and 32.1 kV/mm for a 1.0 mm sample. As a result, the dielectric strength of the additively manufactured plastics evaluated as part of this study was lower than the majority of non-printed plastics by at least 15% (with themore » exception of polycarbonate).« less

Dielectric breakdown of additively manufactured polymeric materials

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

Monzel, W. Jacob; Hoff, Brad W.; Maestas, Sabrina S.

Dielectric strength testing of selected Polyjet-printed polymer plastics was performed in accordance with ASTM D149. This dielectric strength data is compared to manufacturer-provided dielectric strength data for selected plastics printed using the stereolithography (SLA), fused deposition modeling (FDM), and selective laser sintering (SLS) methods. Tested Polyjet samples demonstrated dielectric strengths as high as 47.5 kV/mm for a 0.5 mm thick sample and 32.1 kV/mm for a 1.0 mm sample. As a result, the dielectric strength of the additively manufactured plastics evaluated as part of this study was lower than the majority of non-printed plastics by at least 15% (with themore » exception of polycarbonate).« less

Phase-coherent elastic scattering of electromagnetic waves from a random array of resonant dielectric ridges on a dielectric substrate: Weak roughness limit

NASA Astrophysics Data System (ADS)

Danila, B.; McGurn, A. R.

2005-03-01

A theoretical discussion is given of the diffuse scattering of p -polarized electromagnetic waves from a vacuum-dielectric interface characterized by a one-dimensional disorder in the form of parallel, Gaussian shaped, dielectric ridges positioned at random on a planar semi-infinite dielectric substrate. The parameters of the surface roughness are chosen so that the surface is characterized as weakly rough with a low ridge concentration. The emphasis is on phase coherent features in the speckle pattern of light scattered from the surface. These features are determined from the intensity-intensity correlation function of the speckle pattern and are studied as functions of the frequency of light for frequencies near the dielectric frequency resonances of the ridge material. In the first part of the study, the ridges on the substrate are taken to be identical, made from either GaAs, NaF, or ZnS. The substrate for all cases is CdS. In a second set of studies, the heights and widths of the ridges are statistically distributed. The effects of these different types of randomness on the scattering from the random array of dielectric ridges is determined near the dielectric resonance frequency of the ridge material. The work presented is an extension of studies [A. B. McGurn and R. M. Fitzgerald, Phys. Rev. B 65, 155414 (2002)] that originally treated only the differential reflection coefficient of the diffuse scattering of light (not speckle correlation functions) from a system of identical ridges. The object of the present work is to demonstrate the effects of the dielectric frequency resonances of the ridge materials on the phase coherent features found in the speckle patterns of the diffusely scattered light. The dielectric frequency resonances are shown to enhance the observation of the weak localization of electromagnetic surface waves at the random interface. The frequencies treated in this work are in the infrared. Previous weak localization studies have concentrated mainly on the visible and ultraviolet.

Room temperature magnetoelectric coupling and electrical properties of Ni doped Co - ferrite - PZT nanocomposites

NASA Astrophysics Data System (ADS)

Chakraborty, Sarit; Mandal, S. K.; Dey, P.; Saha, B.

2018-04-01

Multiferroic magnetoelectric materials are very interesting for the researcher for the potential application in device preparation. We have prepared 0.3Ni0.5Co0.5Fe2O4 - 0.7PbZr0.58Ti0.42O3 magnetoelectric nanocomposites through chemical pyrophoric reaction process followed by solid state reaction and represented magnetoelectric coupling coefficient, thermally and magnetically tunable AC electrical properties. For the structural characterization XRD pattern and SEM micrograph have been analyzed. AC electrical properties reveal that the grain boundaries resistances are played dominating role in the conduction process in the system. Dielectric studies are represents that the dielectric polarization is decreased with frequency as well as magnetic field where it increases with increasing temperature. The dielectric profiles also represents the electromechanical resonance at a frequency of ˜183 kHz. High dielectric constant and low dielectric loss at room temperature makes the material very promising for the application of magnetic field sensor devices.

A flexible insulator of a hollow SiO2 sphere and polyimide hybrid for flexible OLEDs.

PubMed

Kim, Min Kyu; Kim, Dong Won; Shin, Dong Wook; Seo, Sang Joon; Chung, Ho Kyoon; Yoo, Ji Beom

2015-01-28

The fabrication of interlayer dielectrics (ILDs) in flexible organic light-emitting diodes (OLEDs) not only requires flexible materials with a low dielectric constant, but also ones that possess the electrical, thermal, chemical, and mechanical properties required for optimal device performance. Porous polymer-silica hybrid materials were prepared to satisfy these requirements. Hollow SiO2 spheres were synthesized using atomic layer deposition (ALD) and a thermal calcination process. The hybrid film, which consists of hollow SiO2 spheres and polyimide, shows a low dielectric constant of 1.98 and excellent thermal stability up to 500 °C. After the bending test for 50 000 cycles, the porous hybrid film exhibits no degradation in its dielectric constant or leakage current. These results indicate that the hybrid film made up of hollow SiO2 spheres and polyimide (PI) is useful as a flexible insulator with a low dielectric constant and high thermal stability for flexible OLEDs.

Fabrication of PVDF-TrFE based bilayered PbTiO{sub 3}/PVDF-TrFE films capacitor

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

Nurbaya, Z., E-mail: nurbayazainal@gmail.com; Razak School of Engineering and Advanced Technology, Universiti Teknologi Malaysia, 54100 Kuala Lumpur; Wahid, M. H.

2016-07-06

Development of high performance capacitor is reaching towards new generation where the ferroelectric materials take places as the active dielectric layer. The motivation of this study is to produce high capacitance device with long life cycle. This was configured by preparing bilayered films where lead titanate as an active dielectric layer and stacked with the top dielectric layer, poly(vinyledenefluoride-trifluoroethylene). Both of them are being referred that have one in common which is ferroelectric behavior. Therefore the combination of ceramic and polymer ferroelectric material could perform optimum dielectric characteristic for capacitor applications. The fabrication was done by simple sol-gel spin coatingmore » method that being varied at spinning speed property for polymer layers, whereas maintaining the ceramic layer. The characterization of PVDF-TrFE/PbTiO3 was performed according to metal-insulator-metal stacked capacitor measurement which includes structural, dielectric, and ferroelectric measurement.« less

Electrical capacitance volume tomography with high contrast dielectrics using a cuboid sensor geometry

NASA Astrophysics Data System (ADS)

Nurge, Mark A.

2007-05-01

An electrical capacitance volume tomography system has been created for use with a new image reconstruction algorithm capable of imaging high contrast dielectric distributions. The electrode geometry consists of two 4 × 4 parallel planes of copper conductors connected through custom built switch electronics to a commercially available capacitance to digital converter. Typical electrical capacitance tomography (ECT) systems rely solely on mutual capacitance readings to reconstruct images of dielectric distributions. This paper presents a method of reconstructing images of high contrast dielectric materials using only the self-capacitance measurements. By constraining the unknown dielectric material to one of two values, the inverse problem is no longer ill-determined. Resolution becomes limited only by the accuracy and resolution of the measurement circuitry. Images were reconstructed using this method with both synthetic and real data acquired using an aluminium structure inserted at different positions within the sensing region. Comparisons with standard two-dimensional ECT systems highlight the capabilities and limitations of the electronics and reconstruction algorithm.

Electrical capacitance volume tomography of high contrast dielectrics using a cuboid geometry

NASA Astrophysics Data System (ADS)

Nurge, Mark A.

An Electrical Capacitance Volume Tomography system has been created for use with a new image reconstruction algorithm capable of imaging high contrast dielectric distributions. The electrode geometry consists of two 4 x 4 parallel planes of copper conductors connected through custom built switch electronics to a commercially available capacitance to digital converter. Typical electrical capacitance tomography (ECT) systems rely solely on mutual capacitance readings to reconstruct images of dielectric distributions. This dissertation presents a method of reconstructing images of high contrast dielectric materials using only the self capacitance measurements. By constraining the unknown dielectric material to one of two values, the inverse problem is no longer ill-determined. Resolution becomes limited only by the accuracy and resolution of the measurement circuitry. Images were reconstructed using this method with both synthetic and real data acquired using an aluminum structure inserted at different positions within the sensing region. Comparisons with standard two dimensional ECT systems highlight the capabilities and limitations of the electronics and reconstruction algorithm.

Morphological, Raman, electrical and dielectric properties of rare earth doped X-type hexagonal ferrites

NASA Astrophysics Data System (ADS)

Majeed, Abdul; Khan, Muhammad Azhar; ur Raheem, Faseeh; Ahmad, Iftikhar; Akhtar, Majid Niaz; Warsi, Muhammad Farooq

2016-12-01

The influence of rare-earth metals (La, Nd, Gd, Tb, Dy) on morphology, Raman, electrical and dielectric properties of Ba2NiCoRExFe28-xO46 ferrites were studied. The scanning electron microscopy (SEM) exhibited the platelet like structure of these hexagonal ferrites. The surface morphology indicated the formation of ferrite grains in the nano-regime scale. The bands obtained at lower wave number may be attributed to the metal-oxygen vibration at octahedral site which confirm the development of hexagonal phase of these ferrites. The resonance peaks were observed in dielectric constant, dielectric loss factor and quality factor versus frequency graphs. These dielectric parameters indicate that these ferrites nano-materials are potential candidates in the high frequency applications. The enhancement in DC electric resistivity from 2.48×108 to 1.20×109 Ω cm indicates that the prepared materials are beneficial for decreasing the eddy current losses at high frequencies and for the fabrication of multilayer chip inductor (MLCI) devices.

Multiferroics BiMn1-xAlxO3 nanoparticles: Synthesis, characterization and evaluation of various structural, physical, electrical and dielectric parameters

NASA Astrophysics Data System (ADS)

Ahmad, Bashir; Raissat, Rabia; Mumtaz, Saleem; Ahmad, Zahoor; Sadiq, Imran; Ashiq, Muhammad Naeem; Najam-ul-Haq, Muhammad

2017-07-01

The aluminium substituted bismuth based manganates with nominal composition BiMn1-xAlxO3 (x = 0.0, 0.2, 0.4, 0.6 and 0.8) were prepared by the simple microemulsion method. The alteration in their structural, electrical and dielectric parameters due to Al substitution has been investigated. The X-ray diffraction analysis (XRD) confirms the formation of single phase orthorhombic with crystallite size ranges from 32 to 52 nm. The morphological features and particle size were determined by using scanning electron microscopy (SEM). The dc electrical resistivity increased from 6 × 108 to 8 × 109 Ω cm with the increase in substituent concentration. The dielectric constant, dielectric loss tangent and dielectric loss factor decreased with the increase in frequency. The increase in electrical resistivity makes the synthesized materials paramount over other materials and can be useful for technological applications in microwave devices.

A Combined Model of Charging of the Surface and Bulk of a Dielectric Target by Electrons with the Energies 10-30 keV

NASA Astrophysics Data System (ADS)

Zykov, V. M.; Neiman, D. A.

2018-04-01

A physico-mathematical model of the processes of radiation-induced charging of dielectric materials with open surfaces, irradiated with monoenergetic electrons in the energy range 10-30 keV, is described. The model takes into account the relationship between the processes of surface and bulk charging for the given conditions of the experimental design, which accounts for the effect of anomalously long charging of dielectrics after the incident energy of primary electrons during charging is reduced to below the second critical energy for the secondary electronic emission coefficient. The initial fast phase of charging a high-resistivity dielectric material (Al2O3) is investigated. It is shown that as the incident electron energy is approaching the second critical energy during charging, the secondary electronic emission is partially suppressed due to negative charging of the open surface of the dielectric and formation of a near-surface inversion electrical field retarding the electronic emission yield.

Damage free integration of ultralow-k dielectrics by template replacement approach

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

Zhang, L.; De Gendt, S.; Department of Chemistry, Katholieke Universiteit Leuven, 3000 Leuven

2015-08-31

Cu/low-k integration by conventional damascene approach is becoming increasingly difficult as critical dimensions scale down. An alternative integration scheme is studied based on the replacement of a sacrificial template by ultralow-k dielectric. A metal structure is first formed by patterning a template material. After template removal, a k = 2.31 spin-on type of porous low-k dielectric is deposited onto the patterned metal lines. The chemical and electrical properties of spin-on dielectrics are studied on blanket wafers, indicating that during hard bake, most porogen is removed within few minutes, but 120 min are required to achieve the lowest k-value. The effective dielectric constantmore » of the gap-fill low-k is investigated on a 45 nm ½ pitch Meander-Fork structure, leading to k{sub eff} below 2.4. The proposed approach solves the two major challenges in conventional Cu/low-k damascene integration approach: low-k plasma damage and metal penetration during barrier deposition on porous materials.« less

The contribution of 180° domain wall motion to dielectric properties quantified from in situ X-ray diffraction

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

Fancher, C. M.; Brewer, S.; Chung, C. C.

2017-03-01

The contribution of 180° domain wall motion to polarization and dielectric properties of ferroelectric materials has yet to be determined experimentally. In this paper, an approach for estimating the extent of (180°) domain reversal during application of electric fields is presented. We demonstrate this method by determining the contribution of domain reversal to polarization in soft lead zirconate titanate during application of strong electric fields. At the maximum applied field, domain reversal was determined to account for >80% of the measured macroscopic polarization. We also apply the method to quantify the contribution of domain reversal to the weak-field dielectric permittivitymore » of BaTiO 3. The results of this analysis determined that domain reversal accounts for up to ~70% of the macroscopic dielectric permittivity in BaTiO 3. These results demonstrate the predominance of domain reversal to high and low-field dielectric response in ferroelectric polycrystalline materials.« less

Trends in Dielectric Etch for Microelectronics Processing

NASA Astrophysics Data System (ADS)

Hudson, Eric A.

2003-10-01

Dielectric etch technology faces many challenges to meet the requirements for leading-edge microelectronics processing. The move to sub 100-nm device design rules increases the aspect ratios of certain features, imposes tighter restrictions on etched features' critical dimensions, and increases the density of closely packed arrays of features. Changes in photolithography are driving transitions to new photoresist materials and novel multilayer resist methods. The increasing use of copper metallization and low-k interlayer dielectric materials has introduced dual-damascene integration methods, with specialized dielectric etch applications. A common need is the selective removal of multiple layers which have very different compositions, while maintaining close control of the etched features' profiles. To increase productivity, there is a growing trend toward in-situ processing, which allows several films to be successively etched during a single pass through the process module. Dielectric etch systems mainly utilize capacitively coupled etch reactors, operating with medium-density plasmas and low gas residence time. Commercial technology development increasingly relies upon plasma diagnostics and modeling to reduce development cycle time and maximize performance.

THz - ToF Optical Layer Analysis (OLA) to determine optical properties of dielectric materials

NASA Astrophysics Data System (ADS)

Spranger, Holger; Beckmann, Jörg

2017-02-01

Electromagnetic waves with frequencies between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available on the market today which operates with THz-pulses transmitted and received by optically pumped semiconductor antennas. In THz-TDS the travelling time (ToF) and shape of the pulse is changed if it interacts with the dielectric material and its inherent discontinuities. A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. The knowledge of the base materials shape and optical properties is essential for a proper reconstruction result. To obtain these properties a model is assumed which describes the device under the test as multilayer structure composed of thin layers with different dielectric characteristics. The Optical Layer Analysis (OLA) is able to fulfill these requirements. A short description why the optical properties are crucial for meaningful SAFT reconstruction results will be given first. Afterwards the OLA will be derived and applied on representative samples to discuss and evaluate its benefits and limits.

Multi-Scale Modeling of Novel Hall Thrusters: Understanding Physics of CHT and DCF Thrusters

DTIC Science & Technology

2011-12-30

thrusters having over 40 years of flight heritage (the first variant, SPT -50, was flown aboard the Soviet Meteor spacecraft in 1971), the community...symmetric sheath. This finding was touched upon in our previous work.14 The walls of this SPT -type thruster are made of a dielectric material. The...One theory of SPT operation suggests that electron impacts of the dielectric material result in emission of secondary electrons from the material

High voltage photoconductive switch package

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

Caporaso, George J.

2016-11-22

A photoconductive switch having a wide bandgap material substrate between opposing electrodes, and a doped dielectric filler that is in contact with both the electrodes and the substrate at the triple point. The dielectric filler material is doped with a conductive material to make it partially or completely conducting, to minimize the field enhancement near the triple point both when the substrate is not conducting in the "off" state and when the substrate is rendered conducting by radiation in the "on" state.

Design and fabrication of far ultraviolet filters based on π-multilayer technology in high-k materials

PubMed Central

Wang, Xiao-Dong; Chen, Bo; Wang, Hai-Feng; He, Fei; Zheng, Xin; He, Ling-Ping; Chen, Bin; Liu, Shi-Jie; Cui, Zhong-Xu; Yang, Xiao-Hu; Li, Yun-Peng

2015-01-01

Application of π-multilayer technology is extended to high extinction coefficient materials, which is introduced into metal-dielectric filter design. Metal materials often have high extinction coefficients in far ultraviolet (FUV) region, so optical thickness of metal materials should be smaller than that of the dielectric material. A broadband FUV filter of 9-layer non-periodic Al/MgF2 multilayer was successfully designed and fabricated and it shows high reflectance in 140–180 nm, suppressed reflectance in 120–137 nm and 181–220 nm. PMID:25687255

Solar cell contact formation using laser ablation

DOEpatents

Harley, Gabriel; Smith, David D.; Cousins, Peter John

2014-07-22

The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline materiat layer; and forming conductive contacts in the plurality of contact holes.

Low-dielectric constant insulators for future integrated circuits and packages.

PubMed

Kohl, Paul A

2011-01-01

Future integrated circuits and packages will require extraordinary dielectric materials for interconnects to allow transistor advances to be translated into system-level advances. Exceedingly low-permittivity and low-loss materials are required at every level of the electronic system, from chip-level insulators to packages and printed wiring boards. In this review, the requirements and goals for future insulators are discussed followed by a summary of current state-of-the-art materials and technical approaches. Much work needs to be done for insulating materials and structures to meet future needs.

Research on the Crystal Growth and Dielectric Properties of High Permittivity Ferroelectric Materials.

DTIC Science & Technology

1984-05-01

decrease in millimeter wave dielectric losses at low temperatures now makes it imperitive to examine the value of dn/dE from liquid nitrogen up to and...and dielectric losses, with both / decreasing at low temperatures down to 77K for the electric field parallel to the polar axis. The observed changes in...xSrxK -vNa Nb501 5 Crystals at RF and Millimeter Wave Frqutncies ................................. 30 APPENDIX 2 Low and High Frequency Dielectric

Broadband dielectric spectroscopy on single-crystalline and ceramic CaCu3Ti4O12

NASA Astrophysics Data System (ADS)

Krohns, S.; Lunkenheimer, P.; Ebbinghaus, S. G.; Loidl, A.

2007-07-01

The authors present dielectric measurements of the colossal dielectric constant material CaCu3Ti4O12 extending up to 1.3GHz also covering so far only rarely investigated single-crystalline samples. Special emphasis is put on the second relaxation reported in several works on polycrystals, which the authors detect also in single crystals. For polycrystalline samples, the authors provide a recipe to achieve values of the dielectric constant as high as in single crystals.

Optical humidity sensor

DOEpatents

Tarvin, Jeffrey A.

1987-01-01

An optical dielectric humidity sensor which includes a dielectric mirror having multiple alternating layers of two porous water-adsorbent dielectric materials with differing indices of refraction carried by a translucent substrate. A narrow-band polarized light source is positioned to direct light energy onto the mirror, and detectors are positioned to receive light energy transmitted through and reflected by the mirror. A ratiometer indicates humidity in the atmosphere which surrounds the dielectric mirror as a function of a ratio of light energies incident on the detectors.

Optical humidity sensor

DOEpatents

Tarvin, J.A.

1987-02-10

An optical dielectric humidity sensor is disclosed which includes a dielectric mirror having multiple alternating layers of two porous water-adsorbent dielectric materials with differing indices of refraction carried by a translucent substrate. A narrow-band polarized light source is positioned to direct light energy onto the mirror, and detectors are positioned to receive light energy transmitted through and reflected by the mirror. A ratiometer indicates humidity in the atmosphere which surrounds the dielectric mirror as a function of a ratio of light energies incident on the detectors. 2 figs.

Dielectric relaxation of NdMnO{sub 3} nanoparticles

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

Saha, Sujoy, E-mail: sahasujoy3@gmail.com; Chanda, Sadhan; Dutta, Alo

2013-11-15

Graphical abstract: (a) TEM image of particle distribution of NMO. (b) HRTEM image of a single NMO particle under 4,000,000× magnification. (c) SAED pattern of a single NMO nanoparticle. - Highlights: • NdMnO{sub 3} nanoparticles are synthesized by sol–gel process. • TEM micrograph shows a granular characteristic with an average particle size of ∼50 nm. • HRTEM is consistent with the spacing between the (2 0 0) planes of the orthorhombic NdMnO{sub 3}. • Band gap is found to be 4.4 eV. • Cole–Cole model has been used to explain the dielectric relaxation in the material. • The activation energymore » of the material is found to be ∼0.43 eV. - Abstract: The neodymium manganate (NdMnO{sub 3}) nanoparticles are synthesized by the sol–gel process. The phase formation and particle size of the sample are determined by X-ray diffraction analysis and transmission electron microscopy. The band gap of the material is obtained by UV–visible absorption spectroscopy using Tauc relation. Dielectric properties of the sample have been investigated in the frequency range from 42 Hz to 1 MHz and in the temperature range from 303 K to 573 K. The dielectric relaxation peaks are observed in the frequency dependent dielectric loss spectra. The Cole–Cole model is used to explain the dielectric relaxation mechanism of the material. The complex impedance plane plot confirms the existence of both the grain and grain-boundary contribution to the relaxation. The temperature dependence of both grain and grain-boundary resistances follow the Arrhenius law with the activation energy of 0.427 and 0.431 eV respectively. The frequency-dependent conductivity spectra follow the power law.« less

Constraining Bulk Densities of Near-Earth Asteroid Surfaces from Radar Observations Using Laboratory Measurements of Permittivity

NASA Astrophysics Data System (ADS)

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

2017-12-01

Planetary radar is widely used to survey the Near-Earth Asteroid (NEA) population and can provide insight into target shapes, sizes, and spin states. The dual-polarization reflectivity is sensitive to surface roughness as well as material properties, specifically the real part of the complex permittivity, or dielectric constant. Knowledge of the behavior of the dielectric constant of asteroid regolith analogue material with environmental parameters can be used to inversely solve for such parameters, such as bulk density, from radar observations. In this study laboratory measurements of the complex permittivity of powdered aluminum oxide and dunite samples are performed in a low-pressure environment chamber using a coaxial transmission line from roughly 1 GHz to 8.5 GHz. The bulk densities of the samples are varied across the measurements by incrementally adding silica aerogel, a low-density material with a very low dielectric constant. This allows the alteration of the proportions of void space to solid particle grains to achieve microgravity-relevant porosities without significantly altering the dielectric properties of the powder sample. The data are then modeled using various electromagnetic mixing equations to characterize the change in dielectric constant with increasing volume fractions of void space (decreasing bulk density). Using spectral analogues as constraints on the composition of NEAs allows us to calculate the range in bulk densities in the near surface of NEAs that have been observed by planetary radar. Utilizing existing radar data from Arecibo Observatory we calculate the bulk density in the near-surface on (101955) Bennu, the target of NASA's OSIRIS-Rex mission, to be ρ = 1.27 ± 0.33 g cm-3 based on an average of the likely range in particle density and dielectric constant of the regolith material.

Noncontact conductivity and dielectric measurement for high throughput roll-to-roll nanomanufacturing

NASA Astrophysics Data System (ADS)

Orloff, Nathan D.; Long, Christian J.; Obrzut, Jan; Maillaud, Laurent; Mirri, Francesca; Kole, Thomas P.; McMichael, Robert D.; Pasquali, Matteo; Stranick, Stephan J.; Alexander Liddle, J.

2015-11-01

Advances in roll-to-roll processing of graphene and carbon nanotubes have at last led to the continuous production of high-quality coatings and filaments, ushering in a wave of applications for flexible and wearable electronics, woven fabrics, and wires. These applications often require specific electrical properties, and hence precise control over material micro- and nanostructure. While such control can be achieved, in principle, by closed-loop processing methods, there are relatively few noncontact and nondestructive options for quantifying the electrical properties of materials on a moving web at the speed required in modern nanomanufacturing. Here, we demonstrate a noncontact microwave method for measuring the dielectric constant and conductivity (or geometry for samples of known dielectric properties) of materials in a millisecond. Such measurement times are compatible with current and future industrial needs, enabling real-time materials characterization and in-line control of processing variables without disrupting production.

Noncontact conductivity and dielectric measurement for high throughput roll-to-roll nanomanufacturing

PubMed Central

Orloff, Nathan D.; Long, Christian J.; Obrzut, Jan; Maillaud, Laurent; Mirri, Francesca; Kole, Thomas P.; McMichael, Robert D.; Pasquali, Matteo; Stranick, Stephan J.; Alexander Liddle, J.

2015-01-01

Advances in roll-to-roll processing of graphene and carbon nanotubes have at last led to the continuous production of high-quality coatings and filaments, ushering in a wave of applications for flexible and wearable electronics, woven fabrics, and wires. These applications often require specific electrical properties, and hence precise control over material micro- and nanostructure. While such control can be achieved, in principle, by closed-loop processing methods, there are relatively few noncontact and nondestructive options for quantifying the electrical properties of materials on a moving web at the speed required in modern nanomanufacturing. Here, we demonstrate a noncontact microwave method for measuring the dielectric constant and conductivity (or geometry for samples of known dielectric properties) of materials in a millisecond. Such measurement times are compatible with current and future industrial needs, enabling real-time materials characterization and in-line control of processing variables without disrupting production. PMID:26592441

Method for imaging liquid and dielectric materials with scanning polarization force microscopy

DOEpatents

Hu, Jun; Ogletree, D. Frank; Salmeron, Miguel; Xiao, Xudong

1999-01-01

The invention images dielectric polarization forces on surfaces induced by a charged scanning force microscope (SFM) probe tip. On insulators, the major contribution to the surface polarizability at low frequencies is from surface ions. The mobility of these ions depends strongly on the humidity. Using the inventive SFM, liquid films, droplets, and other weakly adsorbed materials have been imaged.

Apparatus for imaging liquid and dielectric materials with scanning polarization force microscopy

DOEpatents

Hu, Jun; Ogletree, D. Frank; Salmeron, Miguel; Xiao, Xudong

1998-01-01

The invention images dielectric polarization forces on surfaces induced by a charged scanning force microscope (SFM) probe tip. On insulators, the major contribution to the surface polarizability at low frequencies is from surface ions. The mobility of these ions depends strongly on the humidity. Using the inventive SFM, liquid films, droplets, and other weakly adsorbed materials have been imaged.

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

Hidayat, Arif, E-mail: arif.hidayat.fmipa@um.ac.id; Latifah, Eny; Kurniati, Diana

This study investigated the influence of refraction index strength on the light propagation in refraction index-varied dielectric material. This dielectric material served as photonic lattice. The behavior of light propagation influenced by variation of refraction index in photonic lattice was investigated. Modes of the guiding light were determined numerically using squared-operator iteration method. It was found that the greater the strength of refraction index, the smaller the guiding modes.

Determination of the reduced matrix of the piezoelectric, dielectric, and elastic material constants for a piezoelectric material with C∞ symmetry.

PubMed

Sherrit, Stewart; Masys, Tony J; Wiederick, Harvey D; Mukherjee, Binu K

2011-09-01

We present a procedure for determining the reduced piezoelectric, dielectric, and elastic coefficients for a C(∞) material, including losses, from a single disk sample. Measurements have been made on a Navy III lead zirconate titanate (PZT) ceramic sample and the reduced matrix of coefficients for this material is presented. In addition, we present the transform equations, in reduced matrix form, to other consistent material constant sets. We discuss the propagation of errors in going from one material data set to another and look at the limitations inherent in direct calculations of other useful coefficients from the data.

Parametric Dielectric Model of Comet Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Heggy, E.; Palmer, E. M.; Kofman, W. W.; Clifford, S. M.; Righter, K.; Herique, A.

2012-12-01

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

Silver (Ag)-Graphene oxide (GO) - Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanostructured composites with high dielectric constant and low dielectric loss

NASA Astrophysics Data System (ADS)

Moharana, Srikanta; Mahaling, Ram Naresh

2017-07-01

The Silver (Ag)-Graphene oxide (GO)-Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) composites were prepared by solution casting techniques and their dielectric properties were measured. Field emission scanning electron microscopy (FESEM) and X-ray analysis (XRD) confirmed that Ag layers were formed on the surface of the Graphene oxide sheets and homogeneously dispersed into the PVDF-HFP matrix. The result showed that the incorporation of Ag-GO nanoparticles greatly improved the dielectric constant value nearly about 65 at 100 Hz, which is comparatively much higher than that of pure PVDF-HFP. Furthermore, the dielectric loss of the composite remained at a low level (<0.1 at 100 Hz). A percolation threshold of 1.5 vol% of Ag-GO was calculated and explained accordingly. The composite having high dielectric constant and low dielectric loss might be used as dielectric materials for electronic capacitors.

A new quadrature annular resonator for 3 T MRI based on artificial-dielectrics.

PubMed

Mikhailovskaya, Anna A; Shchelokova, Alena V; Dobrykh, Dmitry A; Sushkov, Ivan V; Slobozhanyuk, Alexey P; Webb, Andrew

2018-06-01

Dielectric resonators have previously been constructed for ultra-high frequency magnetic resonance imaging and microscopy. However, it is challenging to design these dielectric resonators at clinical field strengths due to their intrinsically large dimensions, especially when using materials with moderate permittivity. Here we propose and characterize a novel approach using artificial-dielectrics which reduces substantially the required outer diameter of the resonator. For a resonator designed to operate in a 3 Tesla scanner using water as the dielectric, a reduction in outer diameter of 37% was achieved. When used in an inductively-coupled wireless mode, the sensitivity of the artificial-dielectric resonator was measured to be slightly higher than that of a standard dielectric resonator operating in its degenerate circularly-polarized hybrid electromagnetic modes (HEM 11 ). This study demonstrates the first application of an artificial-dielectric approach to MR volume coil design. Copyright © 2018 Elsevier Inc. All rights reserved.

A new quadrature annular resonator for 3 T MRI based on artificial-dielectrics

NASA Astrophysics Data System (ADS)

Mikhailovskaya, Anna A.; Shchelokova, Alena V.; Dobrykh, Dmitry A.; Sushkov, Ivan V.; Slobozhanyuk, Alexey P.; Webb, Andrew

2018-06-01

Dielectric resonators have previously been constructed for ultra-high frequency magnetic resonance imaging and microscopy. However, it is challenging to design these dielectric resonators at clinical field strengths due to their intrinsically large dimensions, especially when using materials with moderate permittivity. Here we propose and characterize a novel approach using artificial-dielectrics which reduces substantially the required outer diameter of the resonator. For a resonator designed to operate in a 3 Tesla scanner using water as the dielectric, a reduction in outer diameter of 37% was achieved. When used in an inductively-coupled wireless mode, the sensitivity of the artificial-dielectric resonator was measured to be slightly higher than that of a standard dielectric resonator operating in its degenerate circularly-polarized hybrid electromagnetic modes (HEM11). This study demonstrates the first application of an artificial-dielectric approach to MR volume coil design.

Nanocomposite thin films for optical temperature sensing

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

Ohodnicki, Jr., Paul R.; Brown, Thomas D.; Buric, Michael P.

2017-02-14

The disclosure relates to an optical method for temperature sensing utilizing a temperature sensing material. In an embodiment the gas stream, liquid, or solid has a temperature greater than about 500.degree. C. The temperature sensing material is comprised of metallic nanoparticles dispersed in a dielectric matrix. The metallic nanoparticles have an electronic conductivity greater than approximately 10.sup.-1 S/cm at the temperature of the temperature sensing material. The dielectric matrix has an electronic conductivity at least two orders of magnitude less than the dispersed metallic nanoparticles at the temperature of the temperature sensing material. In some embodiments, the chemical composition ofmore » a gas stream or liquid is simultaneously monitored by optical signal shifts through multiple or broadband wavelength interrogation approaches. In some embodiments, the dielectric matrix provides additional functionality due to a temperature dependent band-edge, an optimized chemical sensing response, or an optimized refractive index of the temperature sensing material for integration with optical waveguides.« less

W-Band Transmission MeasurementS and X-Band Dielectric Properties Measurements for a Radome Material Sample

NASA Technical Reports Server (NTRS)

Cravey, Robin L.; Tiemsin, Pacita I.

1997-01-01

This paper describes measurements which were performed on a sample of radome material in the Electromagnetic Properties Measurements Laboratory (EPML). The purpose of the measurements described in this paper was to determine the one-way transmission loss through the flat panel of radome material for a frequency range of 84 to 94 GHz, for varying incidence angles. The panel, which was manufactured by Norton Performance Plastics Corporation, was provided to the EPML by TRW. The size of the panel is 40 in x 36 in x 0.422 in and consists of a foam material with one side coated with a smooth white coating (this side will be referred to as the front side). The dielectric properties of the foam material from the inside of the panel were also determined at X-band (8.2-12.4 GHz). The W-band free space measurements are presented first, followed by the X-band dielectric properties measurements.

Surface Flashover on Epoxy-Resin Printed Circuit Boards in Vacuum under Electron Irradiation

NASA Astrophysics Data System (ADS)

Fujii, Haruhisa; Hasegawa, Taketoshi; Osuga, Hiroyuki; Matsui, Katsuaki

This paper deals with the surface flashover characteristics of dielectric material in vacuum during electron beam irradiation in order to design adequately the conductive patterns on printed circuit boards used inside a spacecraft. The dielectric material, glass-fiber reinforced epoxy resin, and the electrodes printed on it were irradiated with electrons of the energy of 3-10 keV. DC high voltage was applied between the two electrodes during electron irradiation. The voltage was increased stepwise until the surface flashover occurred on the dielectric material. We obtained the results that the surface flashover voltage increased with the insulation distance between the electrodes but electron irradiation made the flashover voltage lower. The flashover voltage characteristics were obtained as parameters of the electrode distance and the energy of the electron beam.

Spectral characterization of dielectric materials using terahertz measurement systems

NASA Astrophysics Data System (ADS)

Seligman, Jeffrey M.

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

Periodic dielectric structure for production of photonic band gap and method for fabricating the same

DOEpatents

Ozbay, Ekmel; Tuttle, Gary; Michel, Erick; Ho, Kai-Ming; Biswas, Rana; Chan, Che-Ting; Soukoulis, Costas

1995-01-01

A method for fabricating a periodic dielectric structure which exhibits a photonic band gap. Alignment holes are formed in a wafer of dielectric material having a given crystal orientation. A planar layer of elongate rods is then formed in a section of the wafer. The formation of the rods includes the step of selectively removing the dielectric material of the wafer between the rods. The formation of alignment holes and layers of elongate rods and wafers is then repeated to form a plurality of patterned wafers. A stack of patterned wafers is then formed by rotating each successive wafer with respect to the next-previous wafer, and then placing the successive wafer on the stack. This stacking results in a stack of patterned wafers having a four-layer periodicity exhibiting a photonic band gap.

Tungsten-doped thin film materials

DOEpatents

Xiang, Xiao-Dong; Chang, Hauyee; Gao, Chen; Takeuchi, Ichiro; Schultz, Peter G.

2003-12-09

A dielectric thin film material for high frequency use, including use as a capacitor, and having a low dielectric loss factor is provided, the film comprising a composition of tungsten-doped barium strontium titanate of the general formula (Ba.sub.x Sr.sub.1-x)TiO.sub.3, where X is between about 0.5 and about 1.0. Also provided is a method for making a dielectric thin film of the general formula (Ba.sub.x Sr.sub.1-x)TiO.sub.3 and doped with W, where X is between about 0.5 and about 1.0, a substrate is provided, TiO.sub.2, the W dopant, Ba, and optionally Sr are deposited on the substrate, and the substrate containing TiO.sub.2, the W dopant, Ba, and optionally Sr is heated to form a low loss dielectric thin film.

Flexible high-temperature dielectric materials from polymer nanocomposites.

PubMed

Li, Qi; Chen, Lei; Gadinski, Matthew R; Zhang, Shihai; Zhang, Guangzu; Li, Haoyu; Iagodkine, Elissei; Haque, Aman; Chen, Long-Qing; Jackson, Tom; Wang, Qing

2015-07-30

Dielectric materials, which store energy electrostatically, are ubiquitous in advanced electronics and electric power systems. Compared to their ceramic counterparts, polymer dielectrics have higher breakdown strengths and greater reliability, are scalable, lightweight and can be shaped into intricate configurations, and are therefore an ideal choice for many power electronics, power conditioning, and pulsed power applications. However, polymer dielectrics are limited to relatively low working temperatures, and thus fail to meet the rising demand for electricity under the extreme conditions present in applications such as hybrid and electric vehicles, aerospace power electronics, and underground oil and gas exploration. Here we describe crosslinked polymer nanocomposites that contain boron nitride nanosheets, the dielectric properties of which are stable over a broad temperature and frequency range. The nanocomposites have outstanding high-voltage capacitive energy storage capabilities at record temperatures (a Weibull breakdown strength of 403 megavolts per metre and a discharged energy density of 1.8 joules per cubic centimetre at 250 degrees Celsius). Their electrical conduction is several orders of magnitude lower than that of existing polymers and their high operating temperatures are attributed to greatly improved thermal conductivity, owing to the presence of the boron nitride nanosheets, which improve heat dissipation compared to pristine polymers (which are inherently susceptible to thermal runaway). Moreover, the polymer nanocomposites are lightweight, photopatternable and mechanically flexible, and have been demonstrated to preserve excellent dielectric and capacitive performance after intensive bending cycles. These findings enable broader applications of organic materials in high-temperature electronics and energy storage devices.

Flexible high-temperature dielectric materials from polymer nanocomposites

NASA Astrophysics Data System (ADS)

Li, Qi; Chen, Lei; Gadinski, Matthew R.; Zhang, Shihai; Zhang, Guangzu; Li, Haoyu; Haque, Aman; Chen, Long-Qing; Jackson, Tom; Wang, Qing

2015-07-01

Dielectric materials, which store energy electrostatically, are ubiquitous in advanced electronics and electric power systems. Compared to their ceramic counterparts, polymer dielectrics have higher breakdown strengths and greater reliability, are scalable, lightweight and can be shaped into intricate configurations, and are therefore an ideal choice for many power electronics, power conditioning, and pulsed power applications. However, polymer dielectrics are limited to relatively low working temperatures, and thus fail to meet the rising demand for electricity under the extreme conditions present in applications such as hybrid and electric vehicles, aerospace power electronics, and underground oil and gas exploration. Here we describe crosslinked polymer nanocomposites that contain boron nitride nanosheets, the dielectric properties of which are stable over a broad temperature and frequency range. The nanocomposites have outstanding high-voltage capacitive energy storage capabilities at record temperatures (a Weibull breakdown strength of 403 megavolts per metre and a discharged energy density of 1.8 joules per cubic centimetre at 250 degrees Celsius). Their electrical conduction is several orders of magnitude lower than that of existing polymers and their high operating temperatures are attributed to greatly improved thermal conductivity, owing to the presence of the boron nitride nanosheets, which improve heat dissipation compared to pristine polymers (which are inherently susceptible to thermal runaway). Moreover, the polymer nanocomposites are lightweight, photopatternable and mechanically flexible, and have been demonstrated to preserve excellent dielectric and capacitive performance after intensive bending cycles. These findings enable broader applications of organic materials in high-temperature electronics and energy storage devices.

Shellac Films as a Natural Dielectric Layer for Enhanced Electron Transport in Polymer Field-Effect Transistors.

PubMed

Baek, Seung Woon; Ha, Jong-Woon; Yoon, Minho; Hwang, Do-Hoon; Lee, Jiyoul

2018-06-06

Shellac, a natural polymer resin obtained from the secretions of lac bugs, was evaluated as a dielectric layer in organic field-effect transistors (OFETs) on the basis of donor (D)-acceptor (A)-type conjugated semiconducting copolymers. The measured dielectric constant and breakdown field of the shellac layer were ∼3.4 and 3.0 MV/cm, respectively, comparable with those of a poly(4-vinylphenol) (PVP) film, a commonly used dielectric material. Bottom-gate/top-contact OFETs were fabricated with shellac or PVP as the dielectric layer and one of three different D-A-type semiconducting copolymers as the active layer: poly(cyclopentadithiophene- alt-benzothiadiazole) with p-type characteristics, poly(naphthalene-bis(dicarboximide)- alt-bithiophene) [P(NDI2OD-T2)] with n-type characteristics, and poly(dithienyl-diketopyrrolopyrrole- alt-thienothiophene) [P(DPP2T-TT)] with ambipolar characteristics. The electrical characteristics of the fabricated OFETs were then measured. For all active layers, OFETs with a shellac film as the dielectric layer exhibited a better mobility than those with PVP. For example, the mobility of the OFET with a shellac dielectric and n-type P(NDI2OD-T2) active layer was approximately 2 orders of magnitude greater than that of the corresponding OFET with a PVP insulating layer. When P(DPP2T-TT) served as the active layer, the OFET with shellac as the dielectric exhibited ambipolar characteristics, whereas the corresponding OFET with the PVP dielectric operated only in hole-accumulation mode. The total density of states was analyzed using technology computer-aided design simulations. The results revealed that compared with the OFETs with PVP as the dielectric, the OFETs with shellac as the dielectric had a lower trap-site density at the polymer semiconductor/dielectric interface and much fewer acceptor-like trap sites acting as electron traps. These results demonstrate that shellac is a suitable dielectric material for D-A-type semiconducting copolymer-based OFETs, and the use of shellac as a dielectric layer facilitates electron transport at the interface with D-A-type copolymer channels.

Multifunctional Hybrid Multilayer Gate Dielectrics with Tunable Surface Energy for Ultralow-Power Organic and Amorphous Oxide Thin-Film Transistors.

PubMed

Byun, Hye-Ran; You, Eun-Ah; Ha, Young-Geun

2017-03-01

For large-area, printable, and flexible electronic applications using advanced semiconductors, novel dielectric materials with excellent capacitance, insulating property, thermal stability, and mechanical flexibility need to be developed to achieve high-performance, ultralow-voltage operation of thin-film transistors (TFTs). In this work, we first report on the facile fabrication of multifunctional hybrid multilayer gate dielectrics with tunable surface energy via a low-temperature solution-process to produce ultralow-voltage organic and amorphous oxide TFTs. The hybrid multilayer dielectric materials are constructed by iteratively stacking bifunctional phosphonic acid-based self-assembled monolayers combined with ultrathin high-k oxide layers. The nanoscopic thickness-controllable hybrid dielectrics exhibit the superior capacitance (up to 970 nF/cm 2 ), insulating property (leakage current densities <10 -7 A/cm 2 ), and thermal stability (up to 300 °C) as well as smooth surfaces (root-mean-square roughness <0.35 nm). In addition, the surface energy of the hybrid multilayer dielectrics are easily changed by switching between mono- and bifunctional phosphonic acid-based self-assembled monolayers for compatible fabrication with both organic and amorphous oxide semiconductors. Consequently, the hybrid multilayer dielectrics integrated into TFTs reveal their excellent dielectric functions to achieve high-performance, ultralow-voltage operation (< ± 2 V) for both organic and amorphous oxide TFTs. Because of the easily tunable surface energy, the multifunctional hybrid multilayer dielectrics can also be adapted for various organic and inorganic semiconductors, and metal gates in other device configurations, thus allowing diverse advanced electronic applications including ultralow-power and large-area electronic devices.

Characterizations of biodegradable epoxy-coated cellulose nanofibrils (CNF) thin film for flexible microwave applications

Treesearch

Hongyi Mi; Chien-Hao Liu; Tzu-Husan Chang; Jung-Hun Seo; Huilong Zhang; Sang June Cho; Nader Behdad; Zhenqiang Ma; Chunhua Yao; Zhiyong Cai; Shaoqin Gong

2016-01-01

Wood pulp cellulose nanofibrils (CNF) thin film is a novel recyclable and biodegradable material. We investigated the microwave dielectric properties of the epoxy coated-CNF thin film for potential broad applications in flexible high speed electronics. The characterizations of dielectric properties were carried out in a frequency range of 1–10 GHz. The dielectric...

Method and Apparatus for Precisely Applying Large Planar Equi-Biaxial Strains to a Circular Membrane

DTIC Science & Technology

2013-04-01

potential future Army applications. Electronic properties, such as dielectric strength , capacitance, resistance, and inductance, vary significantly and... dielectric strength and resistance are primarily determined by inherent bulk material properties, including microstructure, while shifts in inductance...less and a nominal thickness up to ~1 mm. 15. SUBJECT TERMS large planar equi-biaxial strain, membrane, dielectric elastomers, electromechanical

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

NASA Astrophysics Data System (ADS)

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.

Enhancing dielectric permittivity for energy-storage devices through tricritical phenomenon

PubMed Central

Gao, Jinghui; Wang, Yan; Liu, Yongbin; Hu, Xinghao; Ke, Xiaoqin; Zhong, Lisheng; He, Yuting; Ren, Xiaobing

2017-01-01

Although dielectric energy-storing devices are frequently used in high voltage level, the fast growing on the portable and wearable electronics have been increasing the demand on the energy-storing devices at finite electric field strength. This paper proposes an approach on enhancing energy density under low electric field through compositionally inducing tricriticality in Ba(Ti,Sn)O3 ferroelectric material system with enlarged dielectric response. The optimal dielectric permittivity at tricritical point can reach to εr = 5.4 × 104, and the associated energy density goes to around 30 mJ/cm3 at the electric field of 10 kV/cm, which exceeds most of the selected ferroelectric materials at the same field strength. The microstructure nature for such a tricritical behavior shows polarization inhomogeneity in nanometeric scale, which indicates a large polarizability under external electric field. Further phenomenological Landau modeling suggests that large dielectric permittivity and energy density can be ascribed to the vanishing of energy barrier for polarization altering caused by tricriticality. Our results may shed light on developing energy-storing dielectrics with large permittivity and energy density at low electric field. PMID:28098249

Parameters design of the dielectric elastomer spring-roll bending actuator (Conference Presentation)

NASA Astrophysics Data System (ADS)

Li, Jinrong; Liu, Liwu; Liu, Yanju; Leng, Jinsong

2017-04-01

Dielectric elastomers are novel soft smart material that could deform sustainably when subjected to external electric field. That makes dielectric elastomers promising materials for actuators. In this paper, a spring-roll actuator that would bend when a high voltage is applied was fabricated based on dielectric elastomer. Using such actuators as active parts, the flexible grippers and inchworm-inspired crawling robots were manufactured, which demonstrated some examples of applications in soft robotics. To guide the parameters design of dielectric elastomer based spring-roll bending actuators, the theoretical model of such actuators was established based on thermodynamic theories. The initial deformation and electrical induced bending angle of actuators were formulated. The failure of actuators was also analyzed considering some typical failure modes like electromechanical instability, electrical breakdown, loss of tension and maximum tolerant stretch. Thus the allowable region of actuators was determined. Then the bending angle-voltage relations and failure voltages of actuators with different parameters, including stretches of the dielectric elastomer film, number of active layers, and dimensions of spring, were investigated. The influences of each parameter on the actuator performances were discussed, providing meaningful guidance to the optical design of the spring-roll bending actuators.

High-speed droplet actuation on single-plate electrode arrays.

PubMed

Banerjee, Arghya Narayan; Qian, Shizhi; Joo, Sang Woo

2011-10-15

This paper reports a droplet-based microfluidic device composed of patterned co-planar electrodes in an all-in-a-single-plate arrangement and coated with dielectric layers for electrowetting-on-dielectric (EWOD) actuation of discrete droplets. The co-planar arrangement is preferred over conventional two-plate electrowetting devices because it provides simpler manufacturing process, reduced viscous drag, and easier liquid-handling procedures. These advantages lead to more versatile and efficient microfluidic devices capable of generating higher droplet speed and can incorporate various other droplet manipulation functions into the system for biological, sensing, and other microfluidic applications. We have designed, fabricated, and tested the devices using an insulating layer with materials having relatively high dielectric constant (SiO(2)) and compared the results with polymer coatings (Cytop) with low dielectric constant. Results show that the device with high dielectric layer generates more reproducible droplet transfer over a longer distance with a 25% reduction in the actuation voltage with respect to the polymer coatings, leading to more energy efficient microfluidic applications. We can generate droplet speeds as high as 26 cm/s using materials with high dielectric constant such as SiO(2). Copyright © 2011. Published by Elsevier Inc.

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

Stiubianu, George, E-mail: george.stiubianu@icmpp.ro; Bele, Adrian; Cazacu, Maria

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 rangedmore » 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.« less

Ferroelectric polymer dielectrics: Emerging materials for future electrostatic energy storage applications

NASA Astrophysics Data System (ADS)

Panda, Maheswar

2018-05-01

In this manuscript, the dielectric behavior of a variety of ferroelectric polymer dielectrics (FPD), which may bethe materials for future electrostatic energy storage application shave been discussed. The variety of polymer dielectrics, comprising of ferroelectric polymer[polyvinylidene fluoride (PVDF)]/non-polarpolymer [low density polyethylene (LDPE)] and different sizes of metal particles (Ni, quasicrystal of Al-Cu-Fe) as filler, were prepared through different process conditions (cold press/hot press) and are investigated experimentally. Very high values of effective dielectric constants (ɛeff) with low loss tangent (Tan δ) were observed forall the prepared FPD at their respective percolation thresholds (fc). The enhancement of ɛeff and Tan δ at the insulator to metal transition (IMT) is explained through the boundary layer capacitor effect and the percolation theory respectively. The non-universal fc/critical exponents across the IMT have been explained through percolation theory andis attributed to the fillerparticle size& shape, interaction between the components, method of their preparation, adhesiveness, connectivity and homogeneity, etc. of the samples. Recent results on developed FPD with high ɛeff and low Tan δ prepared through cold press have proven themselves to be the better candidates for low frequency and static dielectric applications.

3D Printed Prisms with Tunable Dispersion for the THz Frequency Range

NASA Astrophysics Data System (ADS)

Busch, Stefan F.; Castro-Camus, Enrique; Beltran-Mejia, Felipe; Balzer, Jan C.; Koch, Martin

2018-04-01

Here, we present a 3D printed prism for THz waves made out of an artificial dielectric material in which the dispersion can be tuned by external compression. The artificial material consists of thin dielectric layers with variable air spacings which has been produced using a fused deposition molding process. The material properties are carefully characterized and the functionality of the prisms is in a good agreement with the underlying theory. These prisms are durable, lightweight, inexpensive, and easy to produce.

3D Printed Prisms with Tunable Dispersion for the THz Frequency Range

NASA Astrophysics Data System (ADS)

Busch, Stefan F.; Castro-Camus, Enrique; Beltran-Mejia, Felipe; Balzer, Jan C.; Koch, Martin

2018-06-01

Here, we present a 3D printed prism for THz waves made out of an artificial dielectric material in which the dispersion can be tuned by external compression. The artificial material consists of thin dielectric layers with variable air spacings which has been produced using a fused deposition molding process. The material properties are carefully characterized and the functionality of the prisms is in a good agreement with the underlying theory. These prisms are durable, lightweight, inexpensive, and easy to produce.

Viking Landers and remote sensing

NASA Technical Reports Server (NTRS)

Moore, H. J.; Jakosky, B. M.; Christensen, P. R.

1987-01-01

Thermal and radar remote sensing signatures of the materials in the lander sample fields can be crudely estimated from evaluations of their physical-mechanical properties, laboratory data on thermal conductivities and dielectric constants, and theory. The estimated thermal inertias and dielectric constants of some of the materials in the sample field are close to modal values estimated from orbital and earth-based observations. This suggests that the mechanical properties of the surface materials of much of Mars will not be significantly different that those of the landing sites.

Investigating Dielectric and Metamaterial Effects in a Terahertz Traveling-Wave Tube Amplifier

NASA Technical Reports Server (NTRS)

Starinshak, David P.; Wilson, Jeffrey D.

2008-01-01

Adding material enhancements to a terahertz traveling-wave tube amplifier is investigated. Isotropic dielectrics, negative-index metamaterials, and anisotropic crystals are simulated, and plans to increase the efficiency of the device are discussed. Early results indicate that adding dielectric to the curved sections of the serpentine-shaped slow-wave circuit produce optimal changes in the cold-test characteristics of the device and a minimal drop in operating frequency. Additional results suggest that materials with simultaneously small relative permittivities and electrical conductivities are best suited for increasing the efficiency of the device. More research is required on the subject, and recommendations are given to determine the direction.

Discharge cell for ozone generator

DOEpatents

Nakatsuka, Suguru

2000-01-01

A discharge cell for use in an ozone generator is provided which can suppress a time-related reduction in ozone concentration without adding a catalytic gas such as nitrogen gas to oxygen gas as a raw material gas. The discharge cell includes a pair of electrodes disposed in an opposed spaced relation with a discharge space therebetween, and a dielectric layer of a three-layer structure consisting of three ceramic dielectric layers successively stacked on at least one of the electrodes, wherein a first dielectric layer of the dielectric layer contacting the one electrode contains no titanium dioxide, wherein a second dielectric layer of the dielectric layer exposed to the discharge space contains titanium dioxide in a metal element ratio of not lower than 10 wt %.

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

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

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

2014-03-24

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

Electrical conduction mechanism and dielectric characterization of MnTPPCl thin films

NASA Astrophysics Data System (ADS)

Meikhail, M. S.; Oraby, A. H.; El-Nahass, M. M.; Zeyada, H. M.; Al-Muntaser, A. A.

2018-06-01

The AC conductivity and dielectric properties of MnTPPCl sandwich structure as Au/MnTPPCl/Au were studied. The conductivity of the MnTPPCl thin films have been interpreted by the correlated barrier hopping (CBH) model. The dominant conduction process have found to be the single polaron hopping conduction. The values of the hopping distance, Rω, barrier height, W, and the localized-state density, N, are estimated at different frequencies. The behavior of dielectric constant and dielectric loss was discussed as a function of temperature and frequency. The dielectric constant was described in terms of polarization mechanism in materials. The spectral behavior of dielectric loss is interpreted on the basis of the Giuntini et al. model [1]. The value of WM is obtained as 0.32 eV. A non-Debye relaxation phenomenon was observed from the dielectric relaxation mechanism.

Synthesis and physical characterization of γ-Fe2O3 and (α+γ)-Fe2O3 nanoparticles

NASA Astrophysics Data System (ADS)

Bhavani, P.; Reddy, N. Ramamanohar; Reddy, I. Venkata Subba

2017-01-01

Magnetic nanoparticles were synthesized at different hydrothermal temperatures (HT; 100, 130, 160 and 190 °C) by using a facile hydrothermal route combined with a subsequent calcination process. The calcined materials were analyzed for phase, microstructure, and magnetic and dielectric properties through different characterization techniques. The structural analyses revealed that the material prepared at a HT of 100 °C and sequentially calcined at 300 °C for 3 h showed a high degree of the maghemite structure. On the other hand calcined materials showed a small additional peak belonging to the hematite structure. FESEM micrographs of the materials calcined at HT, of 100 °C and 190 °C showed spherical-like nanoparticles with diameters in range 30 - 54 nm. Materials prepared at a HT of 160 °C followed by calcination at 300 °C for 3 h exhibited the highest saturation magnetization, Ms = 67 emu/g, with a lower coercivity; all materials were in a single domain state. A high dielectric constant (105.54) was observed for the calcined material that had been prepared at a HT of 130 °C. The dielectric properties of synthesized materials showed an almost frequency-independent behavior.

Dielectric materials for use in thin-film capacitors

NASA Technical Reports Server (NTRS)

Carr, H. E.; Foster, W. D.; Fromhold, A. T., Jr.; Harbuck, T. A.

1969-01-01

Investigation report presents details of dielectric properties of various metals measured at 300 degrees K for thermally evaporated oxides from 300 to 6000 A in thickness. It is relevant to the medium of integrated circuitry.

Method for imaging liquid and dielectric materials with scanning polarization force microscopy

DOEpatents

Hu, J.; Ogletree, D.F.; Salmeron, M.; Xiao, X.

1999-03-09

The invention images dielectric polarization forces on surfaces induced by a charged scanning force microscope (SFM) probe tip. On insulators, the major contribution to the surface polarizability at low frequencies is from surface ions. The mobility of these ions depends strongly on the humidity. Using the inventive SFM, liquid films, droplets, and other weakly adsorbed materials have been imaged. 9 figs.

Apparatus for imaging liquid and dielectric materials with scanning polarization force microscopy

DOEpatents

Hu, J.; Ogletree, D.F.; Salmeron, M.; Xiao, X.

1998-04-28

The invention images dielectric polarization forces on surfaces induced by a charged scanning force microscope (SFM) probe tip. On insulators, the major contribution to the surface polarizability at low frequencies is from surface ions. The mobility of these ions depends strongly on the humidity. Using the inventive SFM, liquid films, droplets, and other weakly adsorbed materials have been imaged. 9 figs.

Reduction of the RCS of the leading edge of a conducting wing-shaped structure by means of lossless dielectric material

NASA Astrophysics Data System (ADS)

Booysen, A. J.; Pistorius, C. W. I.; Malherbe, J. A. G.

1991-06-01

The radar cross section of the leading edge of a conducting wing-shaped structure is reduced by replacing part of the structure with a lossless dielectric material. The structure retains its original external shape, thereby ensuring that the aerodynamic properties are not altered by the structural changes needed to reduce the radar cross section.

Asymmetric Dielectric Elastomer Composite Material

NASA Technical Reports Server (NTRS)

Stewart, Brian K. (Inventor)

2014-01-01

Embodiments of the invention provide a dielectric elastomer composite material comprising a plurality of elastomer-coated electrodes arranged in an assembly. Embodiments of the invention provide improved force output over prior DEs by producing thinner spacing between electrode surfaces. This is accomplished by coating electrodes directly with uncured elastomer in liquid form and then assembling a finished component (which may be termed an actuator) from coated electrode components.

Quantum coherent switch utilizing commensurate nanoelectrode and charge density periodicities

DOEpatents

Harrison,; Neil, Singleton [Santa Fe, NM; John, Migliori [Los Alamos, NM; Albert, [Santa Fe, NM

2008-08-05

A quantum coherent switch having a substrate formed from a density wave (DW) material capable of having a periodic electron density modulation or spin density modulation, a dielectric layer formed onto a surface of the substrate that is orthogonal to an intrinsic wave vector of the DW material; and structure for applying an external spatially periodic electrostatic potential over the dielectric layer.

Studying dielectric mechanism and magnetization of double perovskite Gd2NiMnO6 ceramic

NASA Astrophysics Data System (ADS)

Mohapatra, S. R.; Sahu, B.; Kaushik, S. D.; Singh, A. K.

2016-05-01

In the present work, the structure, dielectric and magnetic properties of Gd2NiMnO6 double perovskite have been studied. X-Ray diffraction study reveals the phase pure formation of the material that crystallizes into monoclinic phase (space group 'P21/n'). Surface morphology depicts heterogeneous grain distribution with average grain size of ~1 µm. Temperature dependent (50 - 330 K) dielectric measurements at different frequencies (0.5 - 50 kHz) relate to Maxwell-Wagner interfacial polarization model. Giant dielectric constant at 1 kHz for 300 K (ɛ' ~1900) is noticed as compared to that of 50 K (ɛ' ~10) coupled with a peak shift in tan loss towards higher temperature with frequency. The activation energy (0.24 eV) obtained using Arrhenius relation for thermally activated relaxor behavior of the material signifies an electron hopping mechanism between Ni2+ and Mn4+ cations. Lastly, M-H study shows `S' shape hysteresis loop at 50 K with remnant magnetization (Mr) of 0.72 µB/f.u. along with a linear plot for 300 K which reveals paramagnetic nature of the material.

Synthesis and electrical behavior of Ni-Ti substituted Y-type hexaferrites for high frequency application

NASA Astrophysics Data System (ADS)

Ahmad, Bashir; Ashiq, Muhammad Naeem; Mumtaz, Saleem; Ali, Irshad; Najam-Ul-Haq, Muhmmad; Sadiq, Imran

2018-04-01

This article reports the fabrication of Ni-Ti doped derivatives of Sr2Co2Fe12-2xO22 by economical Sol-gel method. At room temperature X-ray diffraction (XRD) pattern of powder was obtained after sintering at 1050 °C. The XRD analysis revealed the formation of pure Sr-Y hexaferrite phase. It was found that the observed values of dielectric parameters decreased with increasing Ni-Ti substitution. The higher values of dielectric constants and dielectric loss factor at lower frequency were owing to surface charge polarization. In all the samples the resonance peaks were also observed. The observed room temperature DC electrical resistivity found to increase from 1.8x106 to 4.9x109 ohm cm. The observed activation energies values of the fabricated materials are found in 0.52-0.82 eV range. The decrease in dielectric parameters and increase in resistivity of the fabricated samples with substituents suggest these materials have worth application in micro-wave devices as such devices required highly resistive materials.

Complex oxide thin films for microelectronics

NASA Astrophysics Data System (ADS)

Suvorova, Natalya

The rapid scaling of the device dimensions, namely in metal oxide semiconductor field effect transistor (MOSFET), is reaching its fundamental limit which includes the increase in allowable leakage current due to direct tunneling with decrease of physical thickness of SiO2 gate dielectric. The significantly higher relative dielectric constant (in the range 9--25) of the gate dielectric beyond the 3.9 value of silicon dioxide will allow increasing the physical thickness. Among the choices for the high dielectric constant (K) materials for future generation MOSFET application, barium strontium titanate (BST) and strontium titanate (STO) possess one of the highest attainable K values making them the promising candidates for alternative gate oxide. However, the gate stack engineering does not imply the simple replacement of the SiO2 with the new dielectric. Several requirements should be met for successful integration of a new material. The major one is a production of high level of interface states (Dit) compared to that of SiO 2 on Si. An insertion of a thin SiO2 layer prior the growth of high-K thin film is a simple solution that helps to limit reaction with Si substrate and attains a high quality interface. However, the combination of two thin films reduces the overall K of the dielectric stack. An optimization of the SiO2 underlayer in order to maintain the interface quality yet minimize the effect on K is the focus of this work. The results from our study are presented with emphasis on the key process parameters that improve the dielectric film stack. For in-situ growth characterization of BST and STO films sputter deposited on thermally oxidized Si substrates spectroscopic ellipsometry in combination with time of flight ion scattering and recoil spectrometry have been employed. Studies of material properties have been complemented with analytical electron microscopy. To evaluate the interface quality the electrical characterization has been employed using capacitance-voltage and conductance-voltage measurements. Special attention was given to the extraction of static dielectric constant of BST and STO from the multiple film stack. The K value was found to be sensitive to the input parameters such as dielectric constant and thickness of interface layers.

Plasmon analysis and homogenization in plane layered photonic crystals and hyperbolic metamaterials

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

Davidovich, M. V., E-mail: davidovichmv@info.sgu.ru

2016-12-15

Dispersion equations are obtained and analysis and homogenization are carried out in periodic and quasiperiodic plane layered structures consisting of alternating dielectric layers, metal and dielectric layers, as well as graphene sheets and dielectric (SiO{sub 2}) layers. Situations are considered when these structures acquire the properties of hyperbolic metamaterials (HMMs), i.e., materials the real parts of whose effective permittivity tensor have opposite signs. It is shown that the application of solely dielectric layers is more promising in the context of reducing losses.

Resonant frequency of microstrip antennas calculated from TE-excitation of an infinite strip embedded in a grounded dielectric slab

NASA Technical Reports Server (NTRS)

Bailey, M. C.

1979-01-01

The calculation of currents induced by a plane wave normally incident upon an infinite strip embedded in a grounded dielectric slab is used to infer the resonant width (or frequency) of rectangular microstrip antennas. By placing the strip inside the dielectric, the effect of a dielectric cover of the same material as the substrate can be included in the calculation of resonant frequency. A comparison with measured results indicated agreement of 1 percent or better for rectangular microstrip antennas constructed on Teflon-fiberglass substrate.

Thermodynamic potentials in anisotropic and nonlinear dielectrics

NASA Astrophysics Data System (ADS)

Parravicini, Jacopo

2018-07-01

The variation of total energy, entropy, Helmoltz free energy due to the application of a static electric field is calculated and discussed, under suitable conditions, in the case of a dielectric with either anisotropic or nonlinear response. The proposed approach starts from Fröhlich's theory of dielectric thermodynamics and, by analyzing its assumptions, provides a method to generalize it. The obtained relationships can be employed for describing the thermodynamics of different classes of dielectric materials, also in experimental investigations. Specifically, the anisotropy and nonlinearity conditions are considered and relative examples are indicated and discussed.

Structural and dielectric properties of CTAB modified ZrO2 nanoparticles

NASA Astrophysics Data System (ADS)

Sidhu, Gaganpreet Kaur; Tripathi, S. K.; Kumar, Rajesh

2016-05-01

Zirconia (ZrO2) has been considered as one of the most investigated materials among various metal oxides due its outstanding dielectric properties and ionic conduction properties, which is mainly due to its high oxygen ion conduction. ZrO2 nanoparticles were synthesized using surfactant (CTAB) to study the variation of its dielectric behavior at room temperature. Surfactants form a unique class of chemical compounds, because of their remarkable ability to influence the properties of surfaces and interfaces of nanostructures. The dielectric properties of prepared nanoparticles were studied using LCR meter.

Periodic dielectric structure for production of photonic band gap and method for fabricating the same

DOEpatents

Ozbay, E.; Tuttle, G.; Michel, E.; Ho, K.M.; Biswas, R.; Chan, C.T.; Soukoulis, C.

1995-04-11

A method is disclosed for fabricating a periodic dielectric structure which exhibits a photonic band gap. Alignment holes are formed in a wafer of dielectric material having a given crystal orientation. A planar layer of elongate rods is then formed in a section of the wafer. The formation of the rods includes the step of selectively removing the dielectric material of the wafer between the rods. The formation of alignment holes and layers of elongate rods and wafers is then repeated to form a plurality of patterned wafers. A stack of patterned wafers is then formed by rotating each successive wafer with respect to the next-previous wafer, and then placing the successive wafer on the stack. This stacking results in a stack of patterned wafers having a four-layer periodicity exhibiting a photonic band gap. 42 figures.

Effect of organic flux on the colossal dielectric constant of CaCu3Ti4O12 (CCTO)

NASA Astrophysics Data System (ADS)

Razdan, Vishnu; Singh, Abhishek; Arnold, Brad; Choa, Fow-Sen; Kelly, Lisa; Singh, N. B.

2015-05-01

We have used low temperature organics to achieve orientation of the grains of Ca2/3Cu3Ti4O12 (CCTO) compound to increase the resistivity. During the past fifteen years CCTO has been studied extensively for its performance as a dielectric capacitor. We have synthesized and grown large grains of pure Ca2/3Cu3Ti4O12 and doped compound, and studied the dielectric constant and resistivity. The grains were aligned by using a naphthalene-camphor eutectic. CCTO was mixed in the organic melt and oriented by the directional solidification method. This material has different characteristics than pure processed CCTO material. The effect of solidification conditions and its effect on the morphology and the dielectric constant, resistivity and loss tan delta of pure and doped CCTO are described in this article.

Vacuum-barrier window for wide-bandwidth high-power microwave transmission

DOEpatents

Caplan, M.; Shang, C.C.

1996-08-20

A vacuum output window comprises a planar dielectric material with identical systems of parallel ridges and valleys formed in opposite surfaces. The valleys in each surface neck together along parallel lines in the bulk of the dielectric. Liquid-coolant conduits are disposed linearly along such lines of necking and have water or even liquid nitrogen pumped through to remove heat. The dielectric material can be alumina, or its crystalline form, sapphire. The electric-field of a broadband incident megawatt millimeter-wave radio frequency energy is oriented perpendicular to the system of ridges and valleys. The ridges, about one wavelength tall and with a period of about one wavelength, focus the incident energy through in ribbons that squeeze between the liquid-coolant conduits without significant losses over very broad bands of the radio spectrum. In an alternative embodiment, the liquid-coolant conduits are encased in metal within the bulk of the dielectric. 4 figs.

Vacuum-barrier window for wide-bandwidth high-power microwave transmission

DOEpatents

Caplan, Malcolm; Shang, Clifford C.

1996-01-01

A vacuum output window comprises a planar dielectric material with identical systems of parallel ridges and valleys formed in opposite surfaces. The valleys in each surface neck together along parallel lines in the bulk of the dielectric. Liquid-coolant conduits are disposed linearly along such lines of necking and have water or even liquid nitrogen pumped through to remove heat. The dielectric material can be alumina, or its crystalline form, sapphire. The electric-field of a broadband incident megawatt millimeter-wave radio frequency energy is oriented perpendicular to the system of ridges and valleys. The ridges, about one wavelength tall and with a period of about one wavelength, focus the incident energy through in ribbons that squeeze between the liquid-coolant conduits without significant losses over very broad bands of the radio spectrum. In an alternative embodiment, the liquid-coolant conduits are encased in metal within the bulk of the dielectric.

Dielectric and acoustical high frequency characterisation of PZT thin films

NASA Astrophysics Data System (ADS)

Conde, Janine; Muralt, Paul

2010-02-01

Pb(Zr, Ti)O3 (PZT) is an interesting material for bulk acoustic wave resonator applications due to its high electromechanical coupling constant, which would enable fabrication of large bandwidth frequency filters. The major challenge of the PZT solid solution system is to overcome mechanical losses generally observed in PZT ceramics. To increase the understanding of these losses in textured thin films, thin film bulk acoustic resonators (TFBAR's) based on PZT thin films with compositions either in the tetragonal region or at the morphotropic phase boundary and (111) or {100} textures were fabricated and studied up to 2 GHz. The dielectric and elastic materials coefficients were extracted from impedance measurements at the resonance frequency. The dispersion of the dielectric constant was obtained from impedance measurements up to 2 GHz. The films with varying compositions, textures and deposition methods (sol-gel or sputtering) were compared in terms of dielectric and acoustical properties.

Aggregate linear properties of ferroelectric ceramics and polycrystalline thin films: Calculation by the method of effective piezoelectric medium

NASA Astrophysics Data System (ADS)

Pertsev, N. A.; Zembilgotov, A. G.; Waser, R.

1998-08-01

The effective dielectric, piezoelectric, and elastic constants of polycrystalline ferroelectric materials are calculated from single-crystal data by an advanced method of effective medium, which takes into account the piezoelectric interactions between grains in full measure. For bulk BaTiO3 and PbTiO3 polarized ceramics, the dependences of material constants on the remanent polarization are reported. Dielectric and elastic constants are computed also for unpolarized c- and a-textured ferroelectric thin films deposited on cubic or amorphous substrates. It is found that the dielectric properties of BaTiO3 and PbTiO3 polycrystalline thin films strongly depend on the type of crystal texture. The influence of two-dimensional clamping by the substrate on the dielectric and piezoelectric responses of polarized films is described quantitatively and shown to be especially important for the piezoelectric charge coefficient of BaTiO3 films.

Dielectric studies of Graphene and Glass Fiber reinforced composites

NASA Astrophysics Data System (ADS)

Praveen, D.; Shashi Kumar, M. E.; Pramod, R.

2018-02-01

Graphene and E-glass fibres are one of the key materials used currently due to their unique chemical and mechanical properties. Lately graphene has attracted many researchers across academic fraternity as it can yield better properties with lesser reinforcement percentages. The current research emphasizes on the development of graphene-based nanocomposites and its investigation on dielectric applications. The composites were fabricated by adding graphene reinforcements from 1%-3% by weight using conventional Hand-lay process. A thorough investigation was carried out to determine the dielectric behaviour of the nano-composites using impedance analyser according to ASTM standards. The dielectric measurements were carried out in the temperature range of 300K to 400K in a step of 20K. The current research proposes the material for application in capacitor industry as the sample of 2.5% weight fraction showed highest value of K with 14 at 26.1 Hz and 403K.

A facile growth mechanism, structural, optical, dielectric and electrical properties of ZnSe nanosphere via hydrothermal process

NASA Astrophysics Data System (ADS)

Javed, Qurat-Ul-Ain; Baqi, Sabah; Abbas, Hussain; Bibi, Maryam

2017-02-01

Hydrothermal method was chosen as a convenient method to fabricate zinc selenide (ZnSe) nanoparticle materials. The prepared nanospheres were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), where its different properties were observed using UV-visible spectroscopy and LCR meter. It was found that the pure ZnSe nanoparticles have a Zinc blende structure with crystallite size 10.91 nm and in a spherical form with average diameter of 35 nm (before sonication) and 18 nm (after sonication) with wide band gap of 4.28 eV. It was observed that there is inverse relation of frequency with dielectric constant and dielectric loss while AC conductivity grows up by increasing frequency. Such nanostructures were determined to be effectively used in optoelectronic devices as UV detector and in those devices where high-dielectric constant materials are required.

Invited article: Dielectric material characterization techniques and designs of high-Q resonators for applications from micro to millimeter-waves frequencies applicable at room and cryogenic temperatures.

PubMed

Le Floch, Jean-Michel; Fan, Y; Humbert, Georges; Shan, Qingxiao; Férachou, Denis; Bara-Maillet, Romain; Aubourg, Michel; Hartnett, John G; Madrangeas, Valerie; Cros, Dominique; Blondy, Jean-Marc; Krupka, Jerzy; Tobar, Michael E

2014-03-01

Dielectric resonators are key elements in many applications in micro to millimeter wave circuits, including ultra-narrow band filters and frequency-determining components for precision frequency synthesis. Distributed-layered and bulk low-loss crystalline and polycrystalline dielectric structures have become very important for building these devices. Proper design requires careful electromagnetic characterization of low-loss material properties. This includes exact simulation with precision numerical software and precise measurements of resonant modes. For example, we have developed the Whispering Gallery mode technique for microwave applications, which has now become the standard for characterizing low-loss structures. This paper will give some of the most common characterization techniques used in the micro to millimeter wave regime at room and cryogenic temperatures for designing high-Q dielectric loaded cavities.

Photonic crystal light source

DOEpatents

Fleming, James G [Albuquerque, NM; Lin, Shawn-Yu [Albuquerque, NM; Bur, James A [Corrales, NM

2004-07-27

A light source is provided by a photonic crystal having an enhanced photonic density-of-states over a band of frequencies and wherein at least one of the dielectric materials of the photonic crystal has a complex dielectric constant, thereby producing enhanced light emission at the band of frequencies when the photonic crystal is heated. The dielectric material can be a metal, such as tungsten. The spectral properties of the light source can be easily tuned by modification of the photonic crystal structure and materials. The photonic crystal light source can be heated electrically or other heating means. The light source can further include additional photonic crystals that exhibit enhanced light emission at a different band of frequencies to provide for color mixing. The photonic crystal light source may have applications in optical telecommunications, information displays, energy conversion, sensors, and other optical applications.

Processes for multi-layer devices utilizing layer transfer

DOEpatents

Nielson, Gregory N; Sanchez, Carlos Anthony; Tauke-Pedretti, Anna; Kim, Bongsang; Cederberg, Jeffrey; Okandan, Murat; Cruz-Campa, Jose Luis; Resnick, Paul J

2015-02-03

A method includes forming a release layer over a donor substrate. A plurality of devices made of a first semiconductor material are formed over the release layer. A first dielectric layer is formed over the plurality of devices such that all exposed surfaces of the plurality of devices are covered by the first dielectric layer. The plurality of devices are chemically attached to a receiving device made of a second semiconductor material different than the first semiconductor material, the receiving device having a receiving substrate attached to a surface of the receiving device opposite the plurality of devices. The release layer is etched to release the donor substrate from the plurality of devices. A second dielectric layer is applied over the plurality of devices and the receiving device to mechanically attach the plurality of devices to the receiving device.

Dielectric relaxation behavior of colloidal suspensions of palladium nanoparticle chains dispersed in PVP/EG solution.

PubMed

Chen, Zhen; Zhao, Kong-Shuang; Guo, Lin; Feng, Cai-Hong

2007-04-28

Dielectric measurements were carried out on colloidal suspensions of palladium nanoparticle chains dispersed in poly(vinyl pyrrolidone)/ethylene glycol (PVP/EG) solution with different particle volume fractions, and dielectric relaxation with relaxation time distribution and small relaxation amplitude was observed in the frequency range from 10(5) to 10(7) Hz. By means of the method based on logarithmic derivative of the dielectric constant and a numerical Kramers-Kronig transform method, two dielectric relaxations were confirmed and dielectric parameters were determined from the dielectric spectra. The dielectric parameters showed a strong dependence on the volume fraction of palladium nanoparticle chain. Through analyzing limiting conductivity at low frequency, the authors found the conductance percolation phenomenon of the suspensions, and the threshold volume fraction is about 0.18. It was concluded from analyzing the dielectric parameters that the high frequency dielectric relaxation results from interfacial polarization and the low frequency dielectric relaxation is a consequence of counterion polarization. They also found that the dispersion state of the palladium nanoparticle chain in PVP/EG solution is dependent on the particle volume fraction, and this may shed some light on a better application of this kind of materials.

Synthesis, morphological, electromechanical characterization of (CaMgFex)Fe1-xTi3O12-δ/PDMS nanocomposite thin films for energy storage application

NASA Astrophysics Data System (ADS)

Tripathy, Ashis; Sharma, Priyaranjan; Sahoo, Narayan

2018-03-01

At the present time, flexible and stretchable electronics has intended to use the new cutting-edge technologies for advanced electronic application. Currently, Polymers are being employed for such applications but they are not effective due to their low dielectric constant. To enhance the dielectric properties of polymer for energy storage application, it is necessary to add ceramic material of high dielectric constant to synthesize a polymer-ceramic composite. Therefore, a novel attempt has been made to enhance the dielectric properties of the Polydimethylsiloxane (PDMS) polymer by adding (CaMgFex)Fe1-xTi3O12-δ(0 90%), which can make it a potential material for advanced flexible electronic devices, energy storage and biomedical applications.

Electromagnetic wave energy conversion research

NASA Technical Reports Server (NTRS)

Bailey, R. L.; Callahan, P. S.

1975-01-01

Known electromagnetic wave absorbing structures found in nature were first studied for clues of how one might later design large area man-made radiant-electric converters. This led to the study of the electro-optics of insect dielectric antennae. Insights were achieved into how these antennae probably operate in the infrared 7-14um range. EWEC theoretical models and relevant cases were concisely formulated and justified for metal and dielectric absorber materials. Finding the electromagnetic field solutions to these models is a problem not yet solved. A rough estimate of losses in metal, solid dielectric, and hollow dielectric waveguides indicates future radiant-electric EWEC research should aim toward dielectric materials for maximum conversion efficiency. It was also found that the absorber bandwidth is a theoretical limitation on radiant-electric conversion efficiency. Ideally, the absorbers' wavelength would be centered on the irradiating spectrum and have the same bandwith as the irradiating wave. The EWEC concept appears to have a valid scientific basis, but considerable more research is needed before it is thoroughly understood, especially for the complex randomly polarized, wide band, phase incoherent spectrum of the sun. Specific recommended research areas are identified.

Lightning arrestor connector lead magnesium niobate qualification pellet test procedures.

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

Tuohig, W.; Mahoney, Patrick A.; Tuttle, Bruce Andrew

2009-02-01

Enhanced knowledge preservation for DOE DP technical component activities has recently received much attention. As part of this recent knowledge preservation effort, improved documentation of the sample preparation and electrical testing procedures for lead magnesium niobate--lead titanate (PMN/PT) qualification pellets was completed. The qualification pellets are fabricated from the same parent powders used to produce PMN/PT lightning arrestor connector (LAC) granules at HWF&T. In our report, the procedures for fired pellet surface preparation, electrode deposition, electrical testing and data recording are described. The dielectric measurements described in our report are an information only test. Technical reasons for selecting the electrodemore » material, electrode size and geometry are presented. The electrical testing is based on measuring the dielectric constant and dissipation factor of the pellet during cooling from 280 C to 220 C. The most important data are the temperature for which the peak dielectric constant occurs (Curie Point temperature) and the peak dielectric constant magnitude. We determined that the peak dielectric constant for our procedure would be that measured at 1 kHz at the Curie Point. Both the peak dielectric constant and the Curie point parameters provide semi-quantitative information concerning the chemical and microstructural homogeneity of the parent material used for the production of PMN/PT granules for LACs. Finally, we have proposed flag limits for the dielectric data for the pellets. Specifically, if the temperature of the peak dielectric constant falls outside the range of 250 C {+-} 30 C we propose that a flag limit be imposed that will initiate communication between production agency and design agency personnel. If the peak dielectric constant measured falls outside the range 25,000 {+-} 10,000 we also propose that a flag limit be imposed.« less

Realizing thin electromagnetic absorbers for wide incidence angles from commercially available planar circuit materials

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

Glover, Brian B; Whites, Kieth W; Radway, Matthew J

2009-01-01

In this study, recent work on engineering R-card surface resistivity with printed metallic patterns is extended to the design of thin electromagnetic absorbers. Thin electromagnetic absorbers for wide incidence angles and both polarizations have recently been computationally verified by Luukkonen et al.. These absorbers are analytically modeled high-impedance surfaces with capacitive arrays of square patches implemented with relatively high dielectric constant and high loss substrate. However, the advantages provided by the accurate analytical model are largely negated by the need to obtain high dielectric constant material with accurately engineered loss. Fig. I(c) illustrates full-wave computational results for an absorber withoutmore » vias engineered as proposed by Luukkonen et al.. Unique values for the dielectric loss are required for different center frequencies. Parameters for the capacitive grid are D=5.0 mm and w=O.l mm for a center frequency of 3.36 GHz. The relative permittivity and thickness is 9.20(1-j0.234) and 1=3.048 mm. Consider a center frequency of5.81 GHz and again 1=3.048 mm, the required parameters for the capacitive grid are D=2.0 mm and w=0.2 mm where the required relative permittivity is now 9.20(1-j0.371) Admittedly, engineered dielectrics are themselves a historically interesting and fruitful research area which benefits today from advances in monolithic fabrication using direct-write of dielectrics with nanometer scale inclusions. However, our objective in the present study is to realize the advantages of the absorber proposed by Luukkonen et al. without resort to engineered lossy dielectrics. Specifically we are restricted to commercially available planer circuit materials without use of in-house direct-write technology or materials engineering capability. The materials considered here are TMM 10 laminate with (35 {mu}lm copper cladding with a complex permittivity 9.20-j0.0022) and Ohmegaply resistor conductor material (maximum 250 {Omega}/sq.). A thin electromagnetic absorber for incidence angles greater than 30deg. but less than 60deg. and both polarizations is computationally demonstrated. This absorber utilizes high-permittivity, low-loss microwave substrate in conjunction with an engineered lossy sheet impedance. The lossy sheet impedance is easily engineered with simple analytical approximations and can be manufactured from commercially available laminate materials on microwave substrate.« less

Three-dimensional periodic dielectric structures having photonic Dirac points

DOEpatents

Bravo-Abad, Jorge; Joannopoulos, John D.; Soljacic, Marin

2015-06-02

The dielectric, three-dimensional photonic materials disclosed herein feature Dirac-like dispersion in quasi-two-dimensional systems. Embodiments include a face-centered cubic (fcc) structure formed by alternating layers of dielectric rods and dielectric slabs patterned with holes on respective triangular lattices. This fcc structure also includes a defect layer, which may comprise either dielectric rods or a dielectric slab with patterned with holes. This defect layer introduces Dirac cone dispersion into the fcc structure's photonic band structure. Examples of these fcc structures enable enhancement of the spontaneous emission coupling efficiency (the .beta.-factor) over large areas, contrary to the conventional wisdom that the .beta.-factor degrades as the system's size increases. These results enable large-area, low-threshold lasers; single-photon sources; quantum information processing devices; and energy harvesting systems.

Complex dielectric constants for selected near-millimeter-wave materials at 245 GHz

NASA Technical Reports Server (NTRS)

Dutta, J. M.; Jones, C. R.; Dave, H.

1986-01-01

A double-beam instrument developed in this laboratory has been used to measure the complex dielectric constant of selected materials at 245 GHz. It is reported here the results for crystalline quartz, fused silica (Spectrosil WF and Dynasil 4000), beryllia (iso-pressed), boron nitride (hot-pressed), and a nickel ferrite (Trans-Tech 2-111). Results are compared with the data obtained by other researchers.

Studying tantalum-based high-κ dielectrics in terms of capacitance measurements

NASA Astrophysics Data System (ADS)

Stojanovska-Georgievska, L.

2016-08-01

The trend of rapid development of microelectronics towards nano-miniaturization dictates the inevitable introduction of dielectrics with high permittivity (high-κ dielectrics), as alternative material for replacing SiO2. Therefore, studying these materials in terms of their characteristics, especially in terms of reliability, is of great importance for proper design and manufacture of devices. In this paper, alteration of capacitance in different frequency regimes is used, in order to determine the overall behavior of the material. Samples investigated here are MOS structures containing nanoscale tantalum based dielectrics. Layers of pure Ta2O5, but also Hf and Ti doped tantalum pentoxide, i.e. Ta2O5:Hf and Ta2O5:Ti are studied here. All samples are considered as ultrathin oxide layers with thicknesses less than 15 nm, obtained by radio frequent sputtering on p-type silicon substrate. Measuring capacitive characteristics enables determination of several specific parameters of the structures. The obtained results for capacitance in accumulation, the thickness and time evolution of the interfacial SiO2 layer, values of flatband and threshold voltage, density of oxide charges, interfacial and border states, and reliability properties favor the possibilities for more intensive use of studied materials in new nanoelectronic technologies.

Improved Dielectric Properties and Energy Storage Density of Poly(vinylidene fluoride-co-hexafluoropropylene) Nanocomposite with Hydantoin Epoxy Resin Coated BaTiO3.

PubMed

Luo, Hang; Zhang, Dou; Jiang, Chao; Yuan, Xi; Chen, Chao; Zhou, Kechao

2015-04-22

Energy storage materials are urgently demanded in modern electric power supply and renewable energy systems. The introduction of inorganic fillers to polymer matrix represents a promising avenue for the development of high energy density storage materials, which combines the high dielectric constant of inorganic fillers with supernal dielectric strength of polymer matrix. However, agglomeration and phase separation of inorganic fillers in the polymer matrix remain the key barriers to promoting the practical applications of the composites for energy storage. Here, we developed a low-cost and environmentally friendly route to modifying BaTiO3 (BT) nanoparticles by a kind of water-soluble hydantoin epoxy resin. The modified BT nanoparticles exhibited homogeneous dispersion in the ferroelectric polymer poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) matrix and strong interfacial adhesion with the polymer matrix. The dielectric constants of the nanocomposites increased significantly with the increase of the coated BT loading, while the dielectric loss of the nanocomposites was still as low as that of the pure P(VDF-HFP). The energy storage density of the nanocomposites was largely enhanced with the coated BT loading at the same electric field. The nanocomposite with 20 vol % BT exhibited an estimated maximum energy density of 8.13 J cm(-3), which was much higher than that of pure P(VDF-HFP) and other dielectric polymers. The findings of this research could provide a feasible approach to produce high energy density materials for practical application in energy storage.

Research Update: Polyimide/CaCu3Ti4O12 nanofiber functional hybrid films with improved dielectric properties

NASA Astrophysics Data System (ADS)

Yang, Yang; Wang, Ziyu; Ding, Yi; Lu, Zhihong; Sun, Haoliang; Li, Ya; Wei, Jianhong; Xiong, Rui; Shi, Jing; Liu, Zhengyou; Lei, Qingquan

2013-11-01

This work reports the excellent dielectric properties of polyimide (PI) embedded with CaCu3Ti4O12 (CCTO) nanofibers. The dielectric behaviors were investigated over a frequency of 100 Hz-1 MHz. It is shown that embedding CCTO nanofibers with high aspect ratio (67) is an effective means to enhance the dielectric permittivity and reduce the percolation threshold. The dielectric permittivity of PI/CCTO nanofiber composites is 85 with 1.5 vol.% loading of filler, also the dielectric loss is only 0.015 at 100 Hz. Monte Carlo simulation was used to investigate the percolation threshold of CCTO nanofibers reinforced polyimide matrix by using excluded volume theory and soft, hard-core models. The results are in good agreement with the percolation theory and the hard-core model can well explain the percolation phenomena in PI/CCTO nanofiber composites. The dielectric properties of the composites will meet the practical requirements for the application in high dielectric constant capacitors and high energy density materials.

Electromagnetic field tapering using all-dielectric gradient index materials.

PubMed

Yi, Jianjia; Piau, Gérard-Pascal; de Lustrac, André; Burokur, Shah Nawaz

2016-07-28

The concept of transformation optics (TO) is applied to control the flow of electromagnetic fields between two sections of different dimensions through a tapering device. The broadband performance of the field taper is numerically and experimentally validated. The taper device presents a graded permittivity profile and is fabricated through three-dimensional (3D) polyjet printing technology using low-cost all-dielectric materials. Calculated and measured near-field mappings are presented in order to validate the proposed taper. A good qualitative agreement is obtained between full-wave simulations and experimental tests. Such all-dielectric taper paves the way to novel types of microwave devices that can be easily fabricated through low-cost additive manufacturing processes.

Spacecraft dielectric material properties and spacecraft charging

NASA Technical Reports Server (NTRS)

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

1986-01-01

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

Effect of gradient dielectric coefficient in a functionally graded material (FGM) substrate on the propagation behavior of love waves in an FGM-piezoelectric layered structure.

PubMed

Cao, Xiaoshan; Shi, Junping; Jin, Feng

2012-06-01

The propagation behavior of Love waves in a layered structure that includes a functionally graded material (FGM) substrate carrying a piezoelectric thin film is investigated. Analytical solutions are obtained for both constant and gradient dielectric coefficients in the FGM substrate. Numerical results show that the gradient dielectric coefficient decreases phase velocity in any mode, and the electromechanical coupling factor significantly increases in the first- and secondorder modes. In some modes, the difference in Love waves' phase velocity between these two types of structure might be more than 1%, resulting in significant differences in frequency of the surface acoustic wave devices.

Dielectric elastomer actuators used for pneumatic valve technology

NASA Astrophysics Data System (ADS)

Giousouf, Metin; Kovacs, Gabor

2013-10-01

Dielectric elastomer actuators have been investigated for applications in the field of pneumatic automation technology. We have developed different valve designs with stacked dielectric elastomer actuators and with integrated high voltage converters. The actuators were made using VHB-4910 material and a stacker machine for automated fabrication of the cylindrical actuators. Typical characteristics of pneumatic valves such as flow rate, power consumption and dynamic behaviour are presented. For valve construction the force and stroke parameters of the dielectric elastomer actuator have been measured. Further, benefits for valve applications using dielectric elastomers are shown as well as their potential operational area. Finally, challenges are discussed that are relevant for the use of elastomer actuators in valves for industrial applications.

Structural, dielectric and impedance studies of polycrystalline La0.6Dy0.2Ca0.2MnO3

NASA Astrophysics Data System (ADS)

Nandan, K. R.; Kumar, A. Ruban

2017-05-01

Polycrystalline materials of Dy doped La1-xCaxMnO3 were prepared by Sol-Gel technique using citric acid as a chelating agent at 900°C. The compound was analyzed by powder X-ray diffraction technique and confirmed to be single phased orthorhombic perovskite structure with space group Pnma. From the dielectric and impedance studies confirmed the existence of dielectric relaxation and presence of space charge were observed from the dielectric constant and impedance plots respectively and confirms the existence of relaxation due to oxygen vacancy. Cole-cole plot confirms the presence of dielectric relaxation and grain contribution in the synthesized sample.

Microwave dielectric properties of inorganic fullerene-like tungsten disulfide nanoparticles

NASA Astrophysics Data System (ADS)

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

2013-01-01

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

Dual-band absorption of mid-infrared metamaterial absorber based on distinct dielectric spacing layers.

PubMed

Zhang, Nan; Zhou, Peiheng; Cheng, Dengmu; Weng, Xiaolong; Xie, Jianliang; Deng, Longjiang

2013-04-01

We present the simulation, fabrication, and characterization of a dual-band metamaterial absorber in the mid-infrared regime. Two pairs of circular-patterned metal-dielectric stacks are employed to excite the dual-band absorption peaks. Dielectric characteristics of the dielectric spacing layer determine energy dissipation in each resonant stack, i.e., dielectric or ohmic loss. By controlling material parameters, both two mechanisms are introduced into our structure. Up to 98% absorption is obtained at 9.03 and 13.32 μm in the simulation, which is in reasonable agreement with experimental results. The proposed structure holds promise for various applications, e.g., thermal radiation modulators and multicolor infrared focal plane arrays.

Liquid Dielectrics in an Inhomogeneous Pulsed Electric Field

NASA Astrophysics Data System (ADS)

Shneider, M. N.; Pekker, M.

2016-08-01

This book comprehensively describes the phenomena that occur in liquid dielectrics under the influence of an inhomogeneous pulsed electric field. Written by leading experts in the field, it is the first of its kind to address numerous potential applications such as the technology of high-voltage insulation in pulsed inhomogeneous fields, and applications related to cavitation development in liquid dielectrics, plasma treatment of different materials and plasma medicine dealing with living cells. Liquid Dielectrics in an Inhomogeneous Pulsed Electric Field is intended for a broad audience, from students to engineers and scientists, who are interested in current research questions in electrodynamics and hydrodynamics of liquid dielectrics. Part of the IOP Plasma Physics Series

An equivalent method of mixed dielectric constant in passive microwave/millimeter radiometric measurement

NASA Astrophysics Data System (ADS)

Su, Jinlong; Tian, Yan; Hu, Fei; Gui, Liangqi; Cheng, Yayun; Peng, Xiaohui

2017-10-01

Dielectric constant is an important role to describe the properties of matter. This paper proposes This paper proposes the concept of mixed dielectric constant(MDC) in passive microwave radiometric measurement. In addition, a MDC inversion method is come up, Ratio of Angle-Polarization Difference(RAPD) is utilized in this method. The MDC of several materials are investigated using RAPD. Brightness temperatures(TBs) which calculated by MDC and original dielectric constant are compared. Random errors are added to the simulation to test the robustness of the algorithm. Keywords: Passive detection, microwave/millimeter, radiometric measurement, ratio of angle-polarization difference (RAPD), mixed dielectric constant (MDC), brightness temperatures, remote sensing, target recognition.

High- k Gate Dielectrics for Emerging Flexible and Stretchable Electronics.

PubMed

Wang, Binghao; Huang, Wei; Chi, Lifeng; Al-Hashimi, Mohammed; Marks, Tobin J; Facchetti, Antonio

2018-05-22

Recent advances in flexible and stretchable electronics (FSE), a technology diverging from the conventional rigid silicon technology, have stimulated fundamental scientific and technological research efforts. FSE aims at enabling disruptive applications such as flexible displays, wearable sensors, printed RFID tags on packaging, electronics on skin/organs, and Internet-of-things as well as possibly reducing the cost of electronic device fabrication. Thus, the key materials components of electronics, the semiconductor, the dielectric, and the conductor as well as the passive (substrate, planarization, passivation, and encapsulation layers) must exhibit electrical performance and mechanical properties compatible with FSE components and products. In this review, we summarize and analyze recent advances in materials concepts as well as in thin-film fabrication techniques for high- k (or high-capacitance) gate dielectrics when integrated with FSE-compatible semiconductors such as organics, metal oxides, quantum dot arrays, carbon nanotubes, graphene, and other 2D semiconductors. Since thin-film transistors (TFTs) are the key enablers of FSE devices, we discuss TFT structures and operation mechanisms after a discussion on the needs and general requirements of gate dielectrics. Also, the advantages of high- k dielectrics over low- k ones in TFT applications were elaborated. Next, after presenting the design and properties of high- k polymers and inorganic, electrolyte, and hybrid dielectric families, we focus on the most important fabrication methodologies for their deposition as TFT gate dielectric thin films. Furthermore, we provide a detailed summary of recent progress in performance of FSE TFTs based on these high- k dielectrics, focusing primarily on emerging semiconductor types. Finally, we conclude with an outlook and challenges section.

Measurement of complex terahertz dielectric properties of polymers using an improved free-space technique

NASA Astrophysics Data System (ADS)

Chang, Tianying; Zhang, Xiansheng; Yang, Chuanfa; Sun, Zhonglin; Cui, Hong-Liang

2017-04-01

The complex dielectric properties of non-polar solid polymer materials were measured in the terahertz (THz) band by a free-space technique employing a frequency-extended vector network analyzer (VNA), and by THz time-domain spectroscopy (TDS). Mindful of THz wave’s unique characteristics, the free-space method for measurement of material dielectric properties in the microwave band was expanded and improved for application in the THz frequency region. To ascertain the soundness and utility of the proposed method, measurements of the complex dielectric properties of a variety of polymers were carried out, including polytetrafluoroethylene (PTFE, known also by the brand name Teflon), polypropylene (PP), polyethylene (PE), and glass fiber resin (Composite Stone). The free-space method relies on the determination of electromagnetic scattering parameters (S-parameters) of the sample, with the gated-reflect-line (GRL) calibration technique commonly employed using a VNA. Subsequently, based on the S-parameters, the dielectric constant and loss characteristic of the sample were calculated by using a Newtonian iterative algorithm. To verify the calculated results, THz TDS technique, which produced Fresnel parameters such as reflection and transmission coefficients, was also used to independently determine the dielectric properties of these polymer samples, with results satisfactorily corroborating those obtained by the free-space extended microwave technique.

Current understanding of structure-processing-property relationships in BaTiO 3-Bi( M)O 3 dielectrics

DOE PAGES

Beuerlein, Michaela A.; Kumar, Nitish; Usher, Tedi -Marie; ...

2016-09-01

Here, as part of a continued push for high permittivity dielectrics suitable for use at elevated operating temperatures and/or large electric fields, modifications of BaTiO 3 with Bi( M)O 3, where M represents a net-trivalent B-site occupied by one or more species, have received a great deal of recent attention. Materials in this composition family exhibit weakly coupled relaxor behavior that is not only remarkably stable at high temperatures and under large electric fields, but is also quite similar across various identities of M. Moderate levels of Bi content (as much as 50 mol%) appear to be crucial to themore » stability of the dielectric response. In addition, the presence of significant Bi reduces the processing temperatures required for densification and increases the required oxygen content in processing atmospheres relative to traditional X7R-type BaTiO 3-based dielectrics. Although detailed understanding of the structure–processing–property relationships in this class of materials is still in its infancy, this article reviews the current state of understanding of the mechanisms underlying the high and stable values of both relative permittivity and resistivity that are characteristic of BaTiO 3-Bi( M)O 3 dielectrics as well as the processing challenges and opportunities associated with these materials.« less

Effect of Fe3O4 addition on dielectric properties of LaFeO3 nano-crystalline materials synthesized by sol-gel method

NASA Astrophysics Data System (ADS)

Laysandra, H.; Triyono, D.

2017-04-01

Dielectric properties of nano-crystalline material LaFeO3.xFe3O4 with x = 0, 0.1, 0.2, 0.3, and 0.4 at.% have been studied by impedance spectroscopy method. LaFeO3 was synthesized by sol-gel method resulting nano-particle. Then, it was mixed with Fe3O4 powder. The mixture powder was pressed to form pellet and then sintered at 1300°C for 1 h to form nano-crystalline of LaFeO3.xFe3O4. X-ray diffraction characterization at room temperature for all samples show two phases i.e. perovskite LaFeO3 (orthorhombic) as a main phase and Fe3O4 (cubic) as second phase. It is found that the crystallite size of main phase increases with addition of Fe3O4 until 0.3 at.%. The electrical properties as a function of temperature (300-500 K) and frequency (100 Hz - 1 MHz) are presented in Nyquist and Bode plots. It is observed that from equivalent circuit and their parameters, dielectrical properties are contributed by grain and grain boundary. The dielectric constant, ε‧ were calculated by parallel plate method and their values reach up to 107 exhibiting typical colossal dielectric constant (CDC) material like behavior.

Electrical Characterization of Semiconductor and Dielectric Materials with a Non-Damaging FastGateTM Probe

NASA Astrophysics Data System (ADS)

Robert, Hillard; William, Howland; Bryan, Snyder

2002-03-01

Determination of the electrical properties of semiconductor materials and dielectrics is highly desirable since these correlate best to final device performance. The properties of SiO2 and high k dielectrics such as Equivalent Oxide Thickness(EOT), Interface Trap Density(Dit), Oxide Effective Charge(Neff), Flatband Voltage Hysteresis(Delta Vfb), Threshold Voltage(VT) and, bulk properties such as carrier density profile and channel dose are all important parameters that require monitoring during front end processing. Conventional methods for determining these parameters involve the manufacturing of polysilicon or metal gate MOS capacitors and subsequent measurements of capacitance-voltage(CV) and/or current-voltage(IV). These conventional techniques are time consuming and can introduce changes to the materials being monitored. Also, equivalent circuit effects resulting from excessive leakage current, series resistance and stray inductance can introduce large errors in the measured results. In this paper, a new method is discussed that provides rapid determination of these critical parameters and is robust against equivalent circuit errors. This technique uses a small diameter(30 micron), elastically deformed probe to form a gate for MOSCAP CV and IV and can be used to measure either monitor wafers or test areas within scribe lines on product wafers. It allows for measurements of dielectrics thinner than 10 Angstroms. A detailed description and applications such as high k dielectrics, will be presented.

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

Atamanik, E.; Thangadurai, V.

We report a comparative study of the dielectric properties of solid-state (ceramic method) synthesized NaNbO{sub 3} (NN), Na{sub 0.75}K{sub 0.25}NbO{sub 3} (K25NN), K{sub 0.5}Na{sub 0.5}NbO{sub 3} (KNN) and some composite materials containing In{sub 2}O{sub 3} and NN or KNN using an AC impedance method. Powder X-ray diffraction (PXRD) was employed to investigate the phase purity. No significant amount of impurity phase was observed for NN, K25NN, and KNN. Substitutions of 10, 15 and 25 mol% In{sup 3+} for Nb{sup 5+} in KNN and NN using solid-state reactions at 1150 deg. C resulted in composite materials. AC impedance studies of NN,more » KNN and K25NN in the temperature range of 500-800 deg. C showed a single semicircle (attributed to the bulk property) in the high-frequency range of 10{sup 3} to 10{sup 6} Hz. The individual contributions from the bulk and grain boundary on the dielectric properties were resolved and quantified from the impedance data. The calculated dielectric values for NN were consistent with previously reported in the literature. 10% Indium based KNN composite materials had the lowest dielectric loss 0.585 and the dielectric constant of 233 at 100 kHz at the temperature of 650 deg. C.« less

Elastomer actuators: systematic improvement in properties by use of composite materials

NASA Astrophysics Data System (ADS)

Molberg, Martin; Leterrier, Yves; Plummer, Christopher J. G.; Löwe, Christiane; Opris, Dorina M.; Clemens, Frank; Månson, Jan-Anders E.

2010-04-01

Dielectric elastomer actuators (DEAs) have attracted increasing attention over the last few years owing to their outstanding properties, e.g. their large actuation strains, high energy density, and pliability, which have opened up a wide spectrum of potential applications in fields ranging from microengineering to medical prosthetics. There is consequently a huge demand for new elastomer materials with improved properties to enhance the performance of DEAs and to overcome the limitations associated with currently available materials, such as the need for high activation voltages and the poor long-term stability. The electrostatic pressure that activates dielectric elastomers can be increased by higher permittivity of the elastomer and thus may lead to lower activation voltages. This has led us to consider composite elastomeric dielectrics based on thermoplastic elastomers or PDMS, and conductive polyaniline or ceramic (soft doped PZT) powder fillers. The potential of such materials and strategies to counter the adverse effects of increased conductivity and elastic modulus are discussed.

Ultrafast Plasmonic Control of Second Harmonic Generation

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

Davidson, Roderick B.; Yanchenko, Anna; Ziegler, Jed I.

Efficient frequency conversion techniques are crucial to the development of plasmonic metasurfaces for information processing and signal modulation. In principle, nanoscale electric-field confinement in nonlinear materials enables higher harmonic conversion efficiencies per unit volume than those attainable in bulk materials. Here we demonstrate efficient second-harmonic generation (SHG) in a serrated nanogap plasmonic geometry that generates steep electric field gradients on a dielectric metasurface. An ultrafast control pulse is used to control plasmon-induced electric fields in a thin-film material with inversion symmetry that, without plasmonic enhancement, does not exhibit an even-order nonlinear optical response. The temporal evolution of the plasmonic near-fieldmore » is characterized with ~100 as resolution using a novel nonlinear interferometric technique. The serrated nanogap is a unique platform in which to investigate optically controlled, plasmonically enhanced harmonic generation in dielectric materials on an ultrafast time scale. Lastly, this metamaterial geometry can also be readily extended to all-optical control of other nonlinear phenomena, such as four-wave mixing and sum- and difference-frequency generation, in a wide variety of dielectric materials.« less

Ultrafast Plasmonic Control of Second Harmonic Generation

DOE PAGES

Davidson, Roderick B.; Yanchenko, Anna; Ziegler, Jed I.; ...

2016-06-01

Efficient frequency conversion techniques are crucial to the development of plasmonic metasurfaces for information processing and signal modulation. In principle, nanoscale electric-field confinement in nonlinear materials enables higher harmonic conversion efficiencies per unit volume than those attainable in bulk materials. Here we demonstrate efficient second-harmonic generation (SHG) in a serrated nanogap plasmonic geometry that generates steep electric field gradients on a dielectric metasurface. An ultrafast control pulse is used to control plasmon-induced electric fields in a thin-film material with inversion symmetry that, without plasmonic enhancement, does not exhibit an even-order nonlinear optical response. The temporal evolution of the plasmonic near-fieldmore » is characterized with ~100 as resolution using a novel nonlinear interferometric technique. The serrated nanogap is a unique platform in which to investigate optically controlled, plasmonically enhanced harmonic generation in dielectric materials on an ultrafast time scale. Lastly, this metamaterial geometry can also be readily extended to all-optical control of other nonlinear phenomena, such as four-wave mixing and sum- and difference-frequency generation, in a wide variety of dielectric materials.« less

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

NASA Astrophysics Data System (ADS)

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.

Nonequal iteration directional filters permit selective clearance of ripples in passband circuits

NASA Technical Reports Server (NTRS)

Kurpis, G. P.

1970-01-01

Modified directional filter is comprised of alternate pairs of dielectric and air gap filter sections with unequal electrical lengths. Filter provides more flexibility in choosing dielectric material thickness and permits switching from specially ground to standard thicknesses.

Localized electrical fine tuning of passive microwave and radio frequency devices

DOEpatents

Findikoglu, Alp T.

2001-04-10

A method and apparatus for the localized electrical fine tuning of passive multiple element microwave or RF devices in which a nonlinear dielectric material is deposited onto predetermined areas of a substrate containing the device. An appropriate electrically conductive material is deposited over predetermined areas of the nonlinear dielectric and the signal line of the device for providing electrical contact with the nonlinear dielectric. Individual, adjustable bias voltages are applied to the electrically conductive material allowing localized electrical fine tuning of the devices. The method of the present invention can be applied to manufactured devices, or can be incorporated into the design of the devices so that it is applied at the time the devices are manufactured. The invention can be configured to provide localized fine tuning for devices including but not limited to coplanar waveguides, slotline devices, stripline devices, and microstrip devices.

Metallic nanoshells with semiconductor cores: optical characteristics modified by core medium properties.

PubMed

Bardhan, Rizia; Grady, Nathaniel K; Ali, Tamer; Halas, Naomi J

2010-10-26

It is well-known that the geometry of a nanoshell controls the resonance frequencies of its plasmon modes; however, the properties of the core material also strongly influence its optical properties. Here we report the synthesis of Au nanoshells with semiconductor cores of cuprous oxide and examine their optical characteristics. This material system allows us to systematically examine the role of core material on nanoshell optical properties, comparing Cu(2)O core nanoshells (ε(c) ∼ 7) to lower core dielectric constant SiO(2) core nanoshells (ε(c) = 2) and higher dielectric constant mixed valency iron oxide nanoshells (ε(c) = 12). Increasing the core dielectric constant increases nanoparticle absorption efficiency, reduces plasmon line width, and modifies plasmon energies. Modifying the core medium provides an additional means of tailoring both the near- and far-field optical properties in this unique nanoparticle system.

Optical sensing of analytes in aqueous solutions with a multiple surface-plasmon-polariton-wave platform

PubMed Central

Swiontek, Stephen E.; Pulsifer, Drew P.; Lakhtakia, Akhlesh

2013-01-01

The commonly used optical sensor based on surface plasmon-polariton wave phenomenon can sense just one chemical, because only one SPP wave can be guided by the interface of a metal and a dielectric material contained in the sensor. Multiple analytes could be detected and/or the sensing reliability for a single analyte could be enhanced, if multiple SPP-wave modes could be excited on a single metal/dielectric interface. For that to happen, the partnering dielectric material must be periodically non-homogeneous. Using a chiral sculptured thin film (CSTF) as that material in a SPP-wave platform, we show that the angular locations of multiple SPP-wave modes shift when the void regions of the CSTF are infiltrated with a fluid. The sensitivities realized in the proof-of-concept experiments are comparable to state-of-research values. PMID:23474988

Dielectric-loaded waveguide circulator for cryogenically cooled and cascaded maser waveguide structures

NASA Technical Reports Server (NTRS)

Clauss, R. C.; Quinn, R. B. (Inventor)

1980-01-01

A dielectrically loaded four port waveguide circulator is used with a reflected wave maser connected to a second port between first and third ports to form one of a plurality of cascaded maser waveguide structures. The fourth port is connected to a waveguide loaded with microwave energy absorbing material. The third (output signal) port of one maser waveguide structure is connected by a waveguide loaded with dielectric material to the first (input) port of an adjacent maser waveguide structure, and the second port is connected to a reflected wave maser by a matching transformer which passes the signal to be amplified into and out of the reflected wavemaser and blocks pumping energy in the reflected wave maser from entering the circulator. A number of cascaded maser waveguide structures are thus housed in a relatively small volume of conductive material placed within a cryogenically cooled magnet assembly.

Atomistic determination of flexoelectric properties of crystalline dielectrics

NASA Astrophysics Data System (ADS)

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 dielectrics, our estimates agree to an order of magnitude with the experimental and theoretical estimates for strontium titanate. For barium titanate however, while our estimates agree to an order of magnitude with existing ab initio calculations, there exists a large discrepancy with experimental estimates. The possible reasons for the observed deviations are discussed.

Technique for Performing Dielectric Property Measurements at Microwave Frequencies

NASA Technical Reports Server (NTRS)

Barmatz, Martin B.; Jackson, Henry W.

2010-01-01

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

Dielectric anomaly and relaxation natures in a Zn-Cr pillar-layered metal-organic framework with cages and channels

NASA Astrophysics Data System (ADS)

Xue, Chen; Yao, Zhi-Yuan; Liu, Shao-Xian; Luo, Hong-Bin; Zou, Yang; Li, Li; Ren, Xiao-Ming

2017-06-01

A bimetallic metal-organic framework (MOF) with the formula [Zn3btc2{Cr3O(isonic)6(H2O)2(OH)}]·(DMF)15.5(H2O)8 (H3btc=1,3,5-benzenetricarboxylic acid; isonic=isonicotinicate) shows a pillar-layered structure. The monolayer consists of hexagon-like rings formed by the [Zn(isonic)2(btc)2] tetrahedral and the consecutive monolayers are pillared by trigonal-prismatic clusters of [Cr3O(isonic)6(H2O)2(OH)]through the remaining binding sites of the Zn2+ ions. DMF and water molecules are confined in the cages and channels. TGA indicates that the lattice DMF and water molecules begin to be released at temperatures above 363 K. Dielectric measurements were carried out in the range of 173-363 K and 1-107 Hz for three successive thermal cycles. The dielectric spectroscopy obtained in the first thermal cycle was different from that observed in the next two thermal cycles, while the dielectric spectra in the last two thermal cycles were almost identical. The dielectric nature of this MOF is discussed in detail for each thermal cycle. Since MOFs are unique host-guest systems in which the structure of the host framework is designable and the guests are exchangeable, it is no doubt those MOFs are materials with a variety of dielectric natures. This study gives a fresh impetus to achieve MOFs-based dielectric materials.

Top-gate dielectric induced doping and scattering of charge carriers in epitaxial graphene

NASA Astrophysics Data System (ADS)

Puls, Conor P.; Staley, Neal E.; Moon, Jeong-Sun; Robinson, Joshua A.; Campbell, Paul M.; Tedesco, Joseph L.; Myers-Ward, Rachael L.; Eddy, Charles R.; Gaskill, D. Kurt; Liu, Ying

2011-07-01

We show that an e-gun deposited dielectric impose severe limits on epitaxial graphene-based device performance based on Raman spectroscopy and low-temperature transport measurements. Specifically, we show from studies of epitaxial graphene Hall bars covered by SiO2 that the measured carrier density is strongly inhomogenous and predominantly induced by charged impurities at the grapheme/dielectric interface that limit mobility via Coulomb interactions. Our work emphasizes that material integration of epitaxial graphene and a gate dielectric is the next major road block towards the realization of graphene-based electronics.

Microslab - Waveguide medium for the future

NASA Astrophysics Data System (ADS)

Sequeira, H. B.

1986-09-01

'Microslab' technology, which has the transmission properties of both microstrip and dielectric slab waveguides, and which is aimed for use in MIMIC devices, is described. The Microslab configuration consists of a guiding layer bonded to a metallized dielectric substrate (slab) and a metallized dielectric rod, with the dielectric material and thicknesses chosen for minimal loss and dispersion and for optimum control of the propagating energy. The propagating energy is confined mainly to the guiding layer. The new technology has been used to couple a GaAs Gunn oscillator directly to a GaAs Microslab network to produce 0.25 mW at 141 GHz.

Gate bias stress in pentacene field-effect-transistors: Charge trapping in the dielectric or semiconductor

NASA Astrophysics Data System (ADS)

Häusermann, R.; Batlogg, B.

2011-08-01

Gate bias stress instability in organic field-effect transistors (OFETs) is a major conceptual and device issue. This effect manifests itself by an undesirable shift of the transfer characteristics and is associated with long term charge trapping. We study the role of the dielectric and the semiconductor separately by producing OFETs with the same semiconductor (pentacene) combined with different dielectrics (SiO2 and Cytop). We show that it is possible to fabricate devices which are immune to gate bias stress. For other material combinations, charge trapping occurs in the semiconductor alone or in the dielectric.

Stress effects in ferroelectric perovskite thin-films

NASA Astrophysics Data System (ADS)

Zednik, Ricardo Johann

The exciting class of ferroelectric materials presents the engineer with an array of unique properties that offer promise in a variety of applications; these applications include infra-red detectors ("night-vision imaging", pyroelectricity), micro-electro-mechanical-systems (MEMS, piezoelectricity), and non-volatile memory (NVM, ferroelectricity). Realizing these modern devices often requires perovskite-based ferroelectric films thinner than 100 nm. Two such technologically important material systems are (Ba,Sr)TiO3 (BST), for tunable dielectric devices employed in wireless communications, and Pb(Zr,Ti)O3 (PZT), for ferroelectric non-volatile memory (FeRAM). In general, the material behavior is strongly influenced by the mechanical boundary conditions imposed by the substrate and surrounding layers and may vary considerably from the known bulk behavior. A better mechanistic understanding of these effects is essential for harnessing the full potential of ferroelectric thin-films and further optimizing existing devices. Both materials share a common crystal structure and similar properties, but face unique challenges due to the design parameters of these different applications. Tunable devices often require very low dielectric loss as well as large dielectric tunability. Present results show that the dielectric response of BST thin-films can either resemble a dipole-relaxor or follow the accepted empirical Universal Relaxation Law (Curie-von Schweidler), depending on temperature. These behaviors in a single ferroelectric thin-film system are often thought to be mutually exclusive. In state-of-the-art high density FeRAM, the ferroelectric polarization is at least as important as the dielectric response. It was found that these properties are significantly affected by moderate biaxial tensile and compressive stresses which reversibly alter the ferroelastic domain populations of PZT at room temperature. The 90-degree domain wall motion observed by high resolution synchrotron x-ray diffraction indicates that a small effective restoring stress of about 1 MPa acts on the domain walls in these nano-crystalline PZT films. This insight allows reversible control of the ferroelectric and dielectric behavior of these important functional oxide materials, with important implications for associated integrated devices.

Strongly nonlinear composite dielectrics: A perturbation method for finding the potential field and bulk effective properties

NASA Astrophysics Data System (ADS)

Blumenfeld, Raphael; Bergman, David J.

1991-10-01

A class of strongly nonlinear composite dielectrics is studied. We develop a general method to reduce the scalar-potential-field problem to the solution of a set of linear Poisson-type equations in rescaled coordinates. The method is applicable for a large variety of nonlinear materials. For a power-law relation between the displacement and the electric fields, it is used to solve explicitly for the value of the bulk effective dielectric constant ɛe to second order in the fluctuations of its local value. A simlar procedure for the vector potential, whose curl is the displacement field, yields a quantity analogous to the inverse dielectric constant in linear dielectrics. The bulk effective dielectric constant is given by a set of linear integral expressions in the rescaled coordinates and exact bounds for it are derived.

Ion distributions in electrolyte confined by multiple dielectric interfaces

NASA Astrophysics Data System (ADS)

Jing, Yufei; Zwanikken, Jos W.; Jadhao, Vikram; de La Cruz, Monica

2014-03-01

The distribution of ions at dielectric interfaces between liquids characterized by different dielectric permittivities is crucial to nanoscale assembly processes in many biological and synthetic materials such as cell membranes, colloids and oil-water emulsions. The knowledge of ionic structure of these systems is also exploited in energy storage devices such as double-layer super-capacitors. The presence of multiple dielectric interfaces often complicates computing the desired ionic distributions via simulations or theory. Here, we use coarse-grained models to compute the ionic distributions in a system of electrolyte confined by two planar dielectric interfaces using Car-Parrinello molecular dynamics simulations and liquid state theory. We compute the density profiles for various electrolyte concentrations, stoichiometric ratios and dielectric contrasts. The explanations for the trends in these profiles and discuss their effects on the behavior of the confined charged fluid are also presented.

Anticipating electrical breakdown in dielectric elastomer actuators

NASA Astrophysics Data System (ADS)

Muffoletto, Daniel P.; Burke, Kevin M.; Zirnheld, Jennifer L.

2013-04-01

The output strain of a dielectric elastomer actuator is directly proportional to the square of its applied electric field. However, since the likelihood of electric breakdown is elevated with an increased applied field, the maximum operating electric field of the dielectric elastomer is significantly derated in systems employing these actuators so that failure due to breakdown remains unlikely even as the material ages. In an effort to ascertain the dielectric strength so that stronger electric fields can be applied, partial discharge testing is used to assess the health of the actuator by detecting the charge that is released when localized instances of breakdown partially bridge the insulator. Pre-stretched and unstretched samples of VHB4910 tape were submerged in dielectric oil to remove external sources of partial discharges during testing, and the partial discharge patterns were recorded just before failure of the dielectric sample.

Heat treatment effects on dielectric properties of SRFe{sub 12}O{sub 19} hexaferrite prepared by an SHS route

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

Panchal, Nital R.; Jotania, Rajshree B., E-mail: natal_panchal@yahoo.co.in, E-mail: rbjotania@gmail.com

2011-07-01

The M-type Strontium Hexaferrite SRFe{sub 12}O{sub 19} particles were prepared by a Self propagating High temperature Synthesis (SHS) route. Precursors were heated under two different conditions: microwave heating for 30 minutes and sintered at 950 deg C for 4 hrs. The dielectric properties: dielectric constant ({epsilon}{sup '}), dielectric loss (tan {delta} ) and ac conductivity ({sigma}{sub ac}) were measured at room temperature in the frequency range from 100 Hz to 2 MHz. The samples present a non-linear behavior for the dielectric constant at 1 kHz, 100 kHz and 2 MHz. The dielectric properties of prepared Strontium Hexaferrite samples were discussedmore » in view of applications as a material for microwave devices, permanent magnets and high density magnetic recording media. (author)« less

Parametric presentation of dielectric function of laser pumped wide-zone semiconductor material: Does this function satisfy the Kramers-Kronig relations?

NASA Astrophysics Data System (ADS)

Zimnyakov, D. A.; Yuvchenko, S. A.; Volchkov, S. S.; Samorodina, T. V.

2018-04-01

Dielectric function of wide-zone semiconductor nanoparticles (titanium dioxide) was studied under the condition of laser pumping at various wavelengths. A closed-aperture z-scan method with simultaneous measurements of the right-anglescattered intensity was used to retrieve the real and imaginary parts of dielectric function in the dependence on the pump intensity. It was found that the efficiency of dielectric function modulation by pumping light strongly depends on detuning of the wavelength of pumping light with respect to the fundamental absorption band of nanoparticles. The ColeCole diagrammatic technique was applied for interpretation of the pump-induced changes of the dielectric function in the optical range. Applicability of the Kramers-Kronig relations for description of the observed behavior of the dielectric function is discussed.

Castable three-dimensional stationary phase for electric field-driven applications

DOEpatents

Shepodd, Timothy J.; Whinnery, Jr., Leroy; Even, Jr., William R.

2005-01-25

A polymer material useful as the porous dielectric medium for microfluidic devices generally and electrokinetic pumps in particular. The polymer material is produced from an inverse (water-in-oil) emulsion that creates a 3-dimensional network characterized by small pores and high internal volume, characteristics that are particularly desirable for the dielectric medium for electrokinetic pumps. Further, the material can be cast-to-shape inside a microchannel. The use of bifunctional monomers provides for charge density within the polymer structure sufficient to support electroosmotic flow. The 3-dimensional polymeric material can also be covalently bound to the channel walls thereby making it suitable for high-pressure applications.

Castable three-dimensional stationary phase for electric field-driven applications

DOEpatents

Shepodd, Timothy J [Livermore, CA; Whinnery, Jr., Leroy; Even, Jr., William R.

2009-02-10

A polymer material useful as the porous dielectric medium for microfluidic devices generally and electrokinetic pumps in particular. The polymer material is produced from an inverse (water-in-oil) emulsion that creates a 3-dimensional network characterized by small pores and high internal volume, characteristics that are particularly desirable for the dielectric medium for electrokinetic pumps. Further, the material can be cast-to-shape inside a microchannel. The use of bifunctional monomers provides for charge density within the polymer structure sufficient to support electroosmotic flow. The 3-dimensional polymeric material can also be covalently bound to the channel walls thereby making it suitable for high-pressure applications.

Porous Materials with Ultralow Optical Constants for Integrated Optical Device Applications

NASA Astrophysics Data System (ADS)

Chen, Hsuen-Li; Hsieh, Chung-I; Cheng, Chao-Chia; Chang, Chia-Pin; Hsu, Wen-Hau; Wang, Way-Seen; Liu, Po-Tsun

2005-07-01

Ultralow dielectric constant (<2.0) porous materials have received much attention as next-generation dielectric materials. In this study, optical properties of porous-methyl-silsesquioxane(MSQ)-like films (porous polysilazane, PPSZ) were characterized for optical waveguide devices applications. Measured results indicate that the refractive index is decreased to approximately 1.320 as the hydration time exceeds 24 h. The measured refractive index is about 1.163 at a wavelength of 1550 nm. PPSZ films have low absorption in the 500 to 2000 nm wavelength regime. Because of their relatively low refractive index and low absorption over a large spectral regime, PPSZ films can be good cladding materials for use in optically integrated devices with many high-refractive-index materials such as silicon oxide, silicon nitride, silicon, and polymers. We demonstrate two structures, ridge waveguides and large-angle Y-branch power splitters, composed of PPSZ and SU8 films to illustrate the use of low dielectric constant (K) cladding materials. The simulation results indicate that the PPSZ films provide better confinement of light. Experimentally, a large-angle Y-branch power splitter with PPSZ cladding can be used to guide waves with the large branching angle of 33.58°.

Performance investigation of bandgap, gate material work function and gate dielectric engineered TFET with device reliability improvement

NASA Astrophysics Data System (ADS)

Raad, Bhagwan Ram; Nigam, Kaushal; Sharma, Dheeraj; Kondekar, P. N.

2016-06-01

This script features a study of bandgap, gate material work function and gate dielectric engineering for enhancement of DC and Analog/RF performance, reduction in the hot carriers effect (HCEs) and drain induced barrier lowering (DIBL) for better device reliability. In this concern, the use of band gap and gate material work function engineering improves the device performance in terms of the ON-state current and suppressed ambipolar behaviour with maintaining the low OFF-state current. With these advantages, the use of gate material work function engineering imposes restriction on the high frequency performance due to increment in the parasitic capacitances and also introduces the hot carrier effects. Hence, the gate dielectric engineering with bandgap and gate material work function engineering are used in this paper to overcome the cons of the gate material work function engineering by obtaining a superior performance in terms of the current driving capability, ambipolar conduction, HCEs, DIBL and high frequency parameters of the device for ultra-low power applications. Finally, the optimization of length for different work function is performed to get the best out of this.

Silicon base plate with low parasitic electrical interference for sensors

NASA Technical Reports Server (NTRS)

Tang, Tony K. (Inventor); Gutierrez, Roman C. (Inventor)

2002-01-01

A microgyroscope has a baseplate made of the same material as the rest of the microgyroscope. The baseplate is a silicon baseplate having a heavily p-doped epilayer covered by a thick dielectric film and metal electrodes. The metal electrodes are isolated from the ground plane by the dielectric. This provides very low parasitic capacitive coupling between the electrodes. The thick dielectric reduces the capacitance between the electrodes and the ground plane.

Imaging performance of an isotropic negative dielectric constant slab.

PubMed

Shivanand; Liu, Huikan; Webb, Kevin J

2008-11-01

The influence of material and thickness on the subwavelength imaging performance of a negative dielectric constant slab is studied. Resonance in the plane-wave transfer function produces a high spatial frequency ripple that could be useful in fabricating periodic structures. A cost function based on the plane-wave transfer function provides a useful metric to evaluate the planar slab lens performance, and using this, the optimal slab dielectric constant can be determined.

Assessing the effects of different dielectrics on environmentally conscious powder-mixed EDM of difficult-to-machine material (WC-Co)

NASA Astrophysics Data System (ADS)

Singh, Jagdeep; Sharma, Rajiv Kumar

2016-12-01

Electrical discharge machining (EDM) is a well-known nontraditional manufacturing process to machine the difficult-to-machine (DTM) materials which have unique hardness properties. Researchers have successfully performed hybridization to improve this process by incorporating powders into the EDM process known as powder-mixed EDM process. This process drastically improves process efficiency by increasing material removal rate, micro-hardness, as well as reducing the tool wear rate and surface roughness. EDM also has some input parameters, including pulse-on time, dielectric levels and its type, current setting, flushing pressure, and so on, which have a significant effect on EDM performance. However, despite their positive influence, investigating the effects of these parameters on environmental conditions is necessary. Most studies demonstrate the use of kerosene oil as dielectric fluid. Nevertheless, in this work, the authors highlight the findings with respect to three different dielectric fluids, including kerosene oil, EDM oil, and distilled water using one-variable-at-a-time approach for machining as well as environmental aspects. The hazard and operability analysis is employed to identify the inherent safety factors associated with powder-mixed EDM of WC-Co.

Effective electromagnetic properties of microheterogeneous materials with surface phenomena

NASA Astrophysics Data System (ADS)

Levin, Valery; Markov, Mikhail; Mousatov, Aleksandr; Kazatchenko, Elena; Pervago, Evgeny

2017-10-01

In this paper, we present an approach to calculate the complex dielectric permittivity of a micro-heterogeneous medium composed of non-conductive solid inclusions embedded into the conductive liquid continuous host. To take into account the surface effects, we approximate the inclusion by a layered ellipsoid consisting of a dielectric core and an infinitesimally thin outer shell corresponding to an electrical double layer (EDL). To predict the effective complex dielectric permittivity of materials with a high concentration of inclusions, we have modified the Effective Field Method (EFM) for the layered ellipsoidal particles with complex electrical properties. We present the results of complex permittivity calculations for the composites with randomly and parallel oriented ellipsoidal inclusions. To analyze the influence of surface polarization, we have accomplished modeling in a wide frequency range for different existing physic-chemical models of double electrical layer. The results obtained show that the tensor of effective complex permittivity of a micro-heterogeneous medium with surface effects has complicate dependences on the component electrical properties, spatial material texture, and the inclusion shape (ellipsoid aspect ratio) and size. The dispersion of dielectric permittivity corresponds to the frequency dependence for individual inclusion of given size, and does not depend on the inclusion concentration.

An all-organic composite actuator material with a high dielectric constant.

PubMed

Zhang, Q M; Li, Hengfeng; Poh, Martin; Xia, Feng; Cheng, Z-Y; Xu, Haisheng; Huang, Cheng

2002-09-19

Electroactive polymers (EAPs) can behave as actuators, changing their shape in response to electrical stimulation. EAPs that are controlled by external electric fields--referred to here as field-type EAPs--include ferroelectric polymers, electrostrictive polymers, dielectric elastomers and liquid crystal polymers. Field-type EAPs can exhibit fast response speeds, low hysteresis and strain levels far above those of traditional piezoelectric materials, with elastic energy densities even higher than those of piezoceramics. However, these polymers also require a high field (>70 V micro m(-1)) to generate such high elastic energy densities (>0.1 J cm(-3); refs 4, 5, 9, 10). Here we report a new class of all-organic field-type EAP composites, which can exhibit high elastic energy densities induced by an electric field of only 13 V micro m(-1). The composites are fabricated from an organic filler material possessing very high dielectric constant dispersed in an electrostrictive polymer matrix. The composites can exhibit high net dielectric constants while retaining the flexibility of the matrix. These all-organic actuators could find applications as artificial muscles, 'smart skins' for drag reduction, and in microfluidic systems for drug delivery.

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

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

Ghodgaonkar, D.K.

1987-01-01

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

Structural, electrical, optical and magneto-electric characteristics of chemically synthesized CaCu3Ti4O12 dielectric ceramics

NASA Astrophysics Data System (ADS)

Parida, Kalpana; Choudhary, R. N. P.

2017-07-01

CaCu3Ti4O12 (CCTO) was prepared by a chemical reaction method. The pellets prepared from the calcined powder of the material were sintered at 1100 °C. Analysis of x-ray diffraction pattern, recorded on CCTO powder, confirms the phase formation of CCTO. Studies of dielectric (ɛ r, tanδ) and impedance parameters using dielectric and impedance spectroscopy of the compound have provided information about the electrical properties and the dielectric relaxation mechanism of the material. Detailed studies on the variation of electrical conductivity (dc) with temperature show semi-conducting nature of the material. Study of frequency (of applied electric field) dependence of ac conductivity at different temperatures suggests that the compound follows the Jonscher’s power law. Complex impedance spectroscopic analysis suggests that the semicircles formed in the Nyquist plot are connected to the grains, grain boundary and interface effects. An optical energy band gap of ~1.9 eV is obtained from the UV-visible absorbance spectrum. The magnetic data related to magneto-electric (ME) coefficient, measured by varying dc bias magnetic field, have been obtained at room temperature.

Epitaxial thin films

DOEpatents

Hunt, Andrew Tye; Deshpande, Girish; Lin, Wen-Yi; Jan, Tzyy-Jiuan

2006-04-25

Epitatial thin films for use as buffer layers for high temperature superconductors, electrolytes in solid oxide fuel cells (SOFC), gas separation membranes or dielectric material in electronic devices, are disclosed. By using CCVD, CACVD or any other suitable deposition process, epitaxial films having pore-free, ideal grain boundaries, and dense structure can be formed. Several different types of materials are disclosed for use as buffer layers in high temperature superconductors. In addition, the use of epitaxial thin films for electrolytes and electrode formation in SOFCs results in densification for pore-free and ideal gain boundary/interface microstructure. Gas separation membranes for the production of oxygen and hydrogen are also disclosed. These semipermeable membranes are formed by high-quality, dense, gas-tight, pinhole free sub-micro scale layers of mixed-conducting oxides on porous ceramic substrates. Epitaxial thin films as dielectric material in capacitors are also taught herein. Capacitors are utilized according to their capacitance values which are dependent on their physical structure and dielectric permittivity. The epitaxial thin films of the current invention form low-loss dielectric layers with extremely high permittivity. This high permittivity allows for the formation of capacitors that can have their capacitance adjusted by applying a DC bias between their electrodes.

Material Science Smart Coatings

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

Rubinstein, A. I.; Sabirianov, R. F.; Namavar, Fereydoon

2014-07-01

The contribution of electrostatic interactions to the free energy of binding between model protein and a ceramic implant surface in the aqueous solvent, considered in the framework of the nonlocal electrostatic model, is calculated as a function of the implant low-frequency dielectric constant. We show that the existence of a dynamically ordered (low-dielectric) interfacial solvent layer at the protein-solvent and ceramic-solvent interface markedly increases charging energy of the protein and ceramic implant, and consequently makes the electrostatic contribution to the protein-ceramic binding energy more favorable (attractive). Our analysis shows that the corresponding electrostatic energy between protein and oxide ceramics dependsmore » nonmonotonically on the dielectric constant of ceramic, ε C. Obtained results indicate that protein can attract electrostatically to the surface if ceramic material has a moderate ε C below or about 35 (in particularly ZrO 2 or Ta 2O 5). This is in contrast to classical (local) consideration of the solvent, which demonstrates an unfavorable electrostatic interaction of protein with typical metal oxide ceramic materials (ε C>10). Thus, a solid implant coated by combining oxide ceramic with a reduced dielectric constant can be beneficial to strengthen the electrostatic binding of the protein-implant complex.« less

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

PubMed

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

2012-08-13

Single-mode plasmonic waveguiding properties of metal nanowires with dielectric substrates are investigated using a finite-element method. Au and Ag are selected as plasmonic materials for nanowire waveguides with diameters down to 5-nm-level. Typical dielectric materials with relatively low to high refractive indices, including magnesium fluoride (MgF2), silica (SiO2), indium tin oxide (ITO) and titanium dioxide (TiO2), are used as supporting substrates. Basic waveguiding properties, including propagation constants, power distributions, effective mode areas, propagation distances and losses are obtained at the typical plasmonic resonance wavelength of 660 nm. Compared to that of a freestanding nanowire, the mode area of a substrate-supported nanowire could be much smaller while maintaining an acceptable propagation length. For example, the mode area and propagation length of a 100-nm-diameter Ag nanowire with a MgF2 substrate are about 0.004 μm2 and 3.4 μm, respectively. The dependences of waveguiding properties on geometric and material parameters of the nanowire-substrate system are also provided. Our results may provide valuable references for waveguiding dielectric-supported metal nanowires for practical applications.

Ultrafast re-structuring of the electronic landscape of transparent dielectrics: new material states (Die-Met)

NASA Astrophysics Data System (ADS)

Gamaly, E. G.; Rode, A. V.

2018-03-01

Swift excitation of transparent dielectrics by ultrashort and highly intense laser pulse leads to ultra-fast re-structuring of the electronic landscape and generates many transient material states, which are continuously reshaped in accord with the changing pulse intensity. These unconventional transient material states, which exhibit simultaneously both dielectric and metallic properties, we termed here as the `Die-Met' states. The excited material is transparent and conductive at the same time. The real part of permittivity of the excited material changes from positive to negative values with the increase of excitation, which affects strongly the interaction process during the laser pulse. When the incident field has a component along the permittivity gradient, the amplitude of the field increases resonantly near the point of zero permittivity, which dramatically changes the interaction mode and increases absorption in a way that is similar to the resonant absorption in plasma. The complex 3D structure of the permittivity makes a transparent part of the excited dielectric (at ɛ 0 > ɛ re > 0) optically active. The electro-magnetic wave gets a twisted trajectory and accrues the geometric phase while passing through such a medium. Both the phase and the rotation of the polarisation plane depend on the 3D permittivity structure. Measuring the transmission, polarisation and the phase of the probe beam allows one to quantitatively identify these new transient states. We discuss the revelations of this effect in different experimental situations and their possible applications.

Multilayer Coextrusion of Polymer Composites to Develop Organic Capacitors

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

Mondy, L.; Mrozek, R.; Rao, R.

Multilayer coextrusion is applied to produce a tape containing layers of alternating electrical properties to demonstrate the potential for using coextrusion to manufacture capacitors. To obtain the desired properties, we develop two filled polymer systems, one for conductive layers and one for dielectric layers. We describe numerical models used to help determine the material and processing parameters that impact processing and layer stability. These models help quantify the critical ratios of densities and viscosities of the two layers to maintain stable layers, as well as the effect of increasing the flow rate of one of the two materials. The conductingmore » polymer is based on polystyrene filled with a blend of low-melting-point eutectic metal and nickel particulate filler, as described by Mrozek et al. (2010). The appropriate concentrations of fillers are determined by balancing measured conductivity with processability in a twin screw extruder. Based on results of the numerical models and estimates of the viscosity of emulsions and suspensions, a dielectric layer composed of polystyrene filled with barium titanate is formulated. Despite the fact that the density of the dielectric filler is less than the metallic filler of the conductive phase, as well as rheological measurements that later showed that the dielectric formulation is not an ideal match to the viscosity of the conductive material, the two materials can be successfully coextruded if the flow rates of the two materials are not identical. A measurable capacitance of the layered structure is obtained.« less

Multilayer Coextrusion of Polymer Composites to Develop Organic Capacitors

DOE PAGES

Mondy, L.; Mrozek, R.; Rao, R.; ...

2015-05-29

Multilayer coextrusion is applied to produce a tape containing layers of alternating electrical properties to demonstrate the potential for using coextrusion to manufacture capacitors. To obtain the desired properties, we develop two filled polymer systems, one for conductive layers and one for dielectric layers. We describe numerical models used to help determine the material and processing parameters that impact processing and layer stability. These models help quantify the critical ratios of densities and viscosities of the two layers to maintain stable layers, as well as the effect of increasing the flow rate of one of the two materials. The conductingmore » polymer is based on polystyrene filled with a blend of low-melting-point eutectic metal and nickel particulate filler, as described by Mrozek et al. (2010). The appropriate concentrations of fillers are determined by balancing measured conductivity with processability in a twin screw extruder. Based on results of the numerical models and estimates of the viscosity of emulsions and suspensions, a dielectric layer composed of polystyrene filled with barium titanate is formulated. Despite the fact that the density of the dielectric filler is less than the metallic filler of the conductive phase, as well as rheological measurements that later showed that the dielectric formulation is not an ideal match to the viscosity of the conductive material, the two materials can be successfully coextruded if the flow rates of the two materials are not identical. A measurable capacitance of the layered structure is obtained.« less

Colossal dielectric constant in PrFeO 3 semiconductor ceramics

NASA Astrophysics Data System (ADS)

Prasad, Bandi Vittal; Rao, G. Narsinga; Chen, J. W.; Babu, D. Suresh

2012-02-01

The perovskite PrFeO 3 ceramics were synthesized via sol-gel method. The dielectric properties and impedance spectroscopy (IS) of these ceramics were studied in the frequency range from 100 Hz to 1000 kHz in the temperature range from 80 K to 300 K. These materials exhibited colossal dielectric constant value of ˜10 4 at room temperature. The response is similar to that observed for relaxorferroelectrics. IS data analysis indicates the ceramics to be electrically heterogeneous semiconductor consisting of semiconducting grains with dielectric constant 30 and more resistive grain boundaries with effective dielectric constant ˜10 4. We conclude, therefore that grain boundary effect is the primary source for the high effective permittivity in PrFeO 3 ceramics.

Water permeation and dielectric breakdown. Water permeability in Pub Tedlar. Pub/Tedlar as a function of temperature and humidity

NASA Technical Reports Server (NTRS)

Orehotsky, J.

1985-01-01

Moisture transport and dielectric breakdown of polyvinyl butyral (PVB), Tedlar, and PVB/Tedlar composites were addressed. Data for the temperature range between 20 and 80 C showed that the moisture flux through the composite is governed by the slower material; and that the composite permeability is intermediate to those of the component material, as predicted by theory. Data for Tedlar at 71 C, showing the dependence of moisture flux on relative humidity, was also presented. Dielectric breakdown data were less precise and less conclusive. The generally applied theoretical model does not match the experimental data. The PVB/Tedlar composite exhibited greater voltage breakdown resistance than either component. Testing of EVA and EVA/Tedlar composites is underway.

Experimentally demonstrate the surface state and optical topological phase transition of one dimensional hyperbolic metamaterials in Otto and KR configuration (Conference Presentation)

NASA Astrophysics Data System (ADS)

Wei, Chih Chung; Un, Leng-Wai; Yen, Ta-Jen

2017-05-01

One-dimension hyperbolic metamaterials (1DHMMs) possess marvelous and considerable applications: hyperlens, spontaneous emission engineering and nonlinear optics. Conventionally, effective medium theory, which is only valid for long wavelength limit, was used to predict and analyze the optical properties and applications. In our previous works, we considered a binary 1DHMM which consists of alternative metallic and dielectric layers, and rigorously demonstrated the existence of surface states and bulk-interface correspondence with the plasmonic band theory from the coupled surface plasmon point of view. In the plasmonic band structure, we can classify 1DHMMs into two classes: metallic-like and dielectric-like, depending on the formation of the surface states with dielectric and metallic material, respectively. Band crossing exists only when the dielectric layers are thicker than the metallic ones, which is independent from the dielectric constants. Furthermore, the 1DHMMs are all metallic-like without band crossing. On the other hand, the 1DHMMs with band crossing are metal-like before the band crossing point, while they are dielectric-like after the band crossing point. In this work, we measure the surface states formed by dielectric material and 1DHMMs with band crossing in Otto configuration. With white light source and fixed incident angle, we measure the reflectance to investigate the existence of the surface states of 1DHMMs with various thickness ratio of metallic to dielectric layers. Conclusively, our results show that the surface states of 1DHMMs exist only when the thickness ratio is larger than 0.15. The disappearance of the surface states indicates the topological phase transition of 1DHMMs. Our experimental results will benefit new applications for manipulating light on the surface of hyperbolic metamaterials.

Dielectric function of InGaAs in the visible

NASA Technical Reports Server (NTRS)

Alterovitz, S. A.; Sieg, R. E.; Yao, H. D.; Snyder, P. G.; Woollam, J. A.; Pamulapati, J.; Bhattacharya, P. K.; Sekula-Moise, P. A.

1990-01-01

Measurements are reported of the dielectric function of thermodynamically stable In(x)Ga(1-x)As in the composition range 0.3 equal to or less than X = to or less than 0.7. The optically thick samples of InGaAs were made by molecular beam epitaxy (MBE) in the range 0.4 = to or less than X = to or less than 0.7 and by metal-organic chemical vapor deposition (MOCVD) for X = 0.3. The MBE made samples, usually 1 micron thick, were grown on semi-insulating InP and included a strain release structure. The MOCVD sample was grown on GaAs and was 2 microns thick. The dielectric functions were measured by variable angle spectroscopic ellipsometry in the range 1.55 to 4.4 eV. The data was analyzed assuming an optically thick InGaAs material with an oxide layer on top. The thickness of this layer was estimated by comparing the results for the InP lattice matched material, i.e., X = 0.53, with results published in the literature. The top oxide layer mathematically for X = 0.3 and X = 0.53 was removed to get the dielectric function of the bare InGaAs. In addition, the dielectric function of GaAs in vacuum, after a protective arsenic layer was removed. The dielectric functions for X = 0, 0.3, and 0.53 together with the X = 1 result from the literature to evaluate an algorithm for calculating the dielectric function of InGaAs for an arbitrary value of X(0 = to or less than X = to or less than 1) were used. Results of the dielectric function calculated using the algorithm were compared with experimental data.

Dielectric function of InGaAs in the visible

NASA Technical Reports Server (NTRS)

Alterovitz, S. A.; Yao, H. D.; Snyder, P. G.; Woolam, J. A.; Pamulapati, J.; Bhattacharya, P. K.; Sekula-Moise, P. A.; Sieg, R. E.

1990-01-01

Measurements are reported of the dielectric function of thermodynamically stable In(x)Ga(1-x)As in the composition range 0.3 equal to or less than X = to or less than 0.7. The optically thick samples of InGaAs were made by molecular beam epitaxy (MBE) in the range 0.4 = to or less than X = to or less than 0.7 and by metal-organic chemical vapor deposition (MOCVD) for X = 0.3. The MBE made samples, usually 1 micron thick, were grown on semi-insulating InP and included a strain release structure. The MOCVD sample was grown on GaAs and was 2 microns thick. The dielectric functions were measured by variable angle spectroscopic ellipsometry in the range 1.55 to 4.4 eV. The data was analyzed assuming an optically thick InGaAs material with an oxide layer on top. The thickness of this layer was estimated by comparing the results for the InP lattice matched material, i.e., X = 0.53, with results published in the literature. The top oxide layer mathematically for X = 0.3 and X = 0.53 was removed to get the dielectric function of the bare InGaAs. In addition, the dielectric function of GaAs in vacuum, after a protective arsenic layer was removed. The dielectric functions for X = 0, 0.3, and 0.53 together with the X = 1 result from the literature to evaluate an algorithm for calculating the dielectric function of InGaAs for an arbitrary value of X (0 = to or less than X = to or less than 1) were used. Results of the dielectric function calculated using the algorithm were compared with experimental data.

Dielectric properties of magnetic-ferroelectric CoO-NaNO2-porous glass nanocomposite

NASA Astrophysics Data System (ADS)

Koroleva, E. Yu.; Burdin, D. Yu.; Kumzerov, Yu. A.; Sysoeva, A. A.; Filimonov, A. V.; Vakhrushev, S. B.

2017-10-01

Dielectric properties of the nanostructured multiferroic composite on the basis of silicate porous glass simultaneously filled with ferromagnetic (cobalt oxide CoO) and ferroelectric (sodium nitrite) materials have been investigated in wide temperature (270-570 K) and frequency (10-1-107 Hz) ranges. The mean diameter of pores in the matrix is 7 ± 1 nm. The magnetic material particles are synthesized directly in the pores of the glass matrix and occupy about 10% of the pore volume. The porous glass is well wetted with NaNO2. The latter easily infiltrates into the glass and occupies 90% of the remaining unfilled pore volume. The dielectric response of matrices filled with both the components together and with each component separately is studied. An analysis of the obtained data makes it possible to reveal the contributions of individual components into the dielectric response of the composite and the influence of the confined geometry on their dielectric properties. It is found that the incorporation of CoO nanoparticles leads to an order of magnitude increase in the dielectric permittivity and electrical conductivity of the two-component composite in comparison with these values for the composite filled solely with sodium nitrite and to a decrease in the activation energy over the entire studied temperature range. These studies are of interest not only as a preliminary investigation prior to the study of the effect of a magnetic field on the dielectric properties of the synthesized composite, but are of independent physical interest as well, since they allow one to determine the influence of the confined geometry on the dielectric properties of magnetic metal oxides and on the of their phase transition parameters.

Development of an Ultra-Wideband Circularly Polarized Multiple Layer Dielectric Rod Antenna Design

NASA Astrophysics Data System (ADS)

Wainwright, Gregory D.

This dissertations focuses on the development of a novel Ultra-Wideband (UWB) circularly polarized dielectric rod antenna (CPDRA) which yields a constant gain, pattern, and phase center. These properties are important in many applications. Within radar systems a constant phase center is desirable to avoid errors within downrange and crossrange measurements. In a reflector antenna the illumination, spillover, and phase efficiencies will remain the same over an ultra-wideband. Lastly, near field probes require smooth amplitude and phase patterns over frequency to avoid errors during the calibration process of the antenna under test. In this dissertation a novel CP feeding network has been developed for an ultra-wideband dielectric rod antenna. Circularly-polarized antennas have a major advantage over its linearly-polarized counterpart in that the polarization mismatch loss caused by misalignment between the polarizations of the incident fields and antenna can be avoided. This is important in satellite communications and broadcasts where signal propagation through the ionosphere can experience Faraday Rotation. A circularly polarized antenna is also helpful in mobile radar and communication systems where the receiving antennas orientation is not fixed. Previous research on UWB dielectric rod antenna designs has focused on Dual linear feeds. Each polarization within the dual linear feed is excited by a pair of linear launcher arms fed with a 0°-180° hybrid balun. The proposed CPDRA design does not require the 0°-180° hybrid baluns or 0°-90° hybrid for achieving CP operation. These hybrids will increase the antennas size, weight, cost, and reduce operational bandwidth. A design technique has been developed for an UWB multilayer dielectric waveguide used in a CPDRA antenna. This design technique uses near-field Electric field data from inside the waveguide, in conjunction with a genetic algorithm optimization to yield a wideband waveguide with a near field amplitude distribution that scales with frequency. A multilayered dielectric waveguide presents many fabrication challenges. The thermal expansion rates, moisture absorption rates, and vibration properties differ within the various dielectric materials used. Therefore, the development of a wideband waveguide using one material with a low dielectric constant would be advantages since 3-D printing technology can be utilized. In this dissertation novel TE01 and TM01 mode suppressors have been developed using only a single dielectric material.

Plasma treatment of polymer dielectric films to improve capacitive energy storage

NASA Technical Reports Server (NTRS)

Yializis, A.; Binder, M.; Mammone, R. J.

1994-01-01

Demand for compact instrumentation, portable field equipment, and new electromagnetic weapons is creating a need for new dielectric materials with higher energy storage capabilities. Recognizing the need for higher energy storage capacitors, the Army Research Lab at Fort Monmouth, NJ, initiated a program a year ago to investigate potential methods for increasing the dielectric strength of polyvinylidene difluoride (PVDF) film, which is the highest energy density material commercially available today. Treatment of small area PVDF films in a CF4/O2 plasma showed that the dielectric strength of PVDF films can be increased by as much as 20 percent when treated in a 96 percent CF4/4 percent O2 plasma. This 44 percent increase in energy storage of a PVDF capacitor is significant considering that the treatment can be implemented in a conventional metallizing chamber, with minimum capital investment. The data shows that improved breakdown strength may be unique to PVDF film and the particular CF4/O2 gas mixture, because PVDF film treated with 100 percent CF4, 100 percent O2, Ar gas plasma, and electron irradiation shows no improvement in breakdown strength. Other data presented includes dissipation factor, dielectric constant, and surface tension measurements.

Phase modification and dielectric properties of a cullet-paper ash-kaolin clay-based ceramic

NASA Astrophysics Data System (ADS)

Samah, K. A.; Sahar, M. R.; Yusop, M.; Omar, M. F.

2018-03-01

Novel ceramics from waste material made of ( x) paper ash-(80 - x) cullet-20 kaolin clay (10wt% ≤ x ≤ 30wt%) were successfully synthesized using a conventional solid-state reaction technique. Energy-dispersive X-ray analysis confirmed the presence of Si, Ca, Al, and Fe in the waste material for preparing these ceramics. The influence of the cullet content on the phase structures and the dielectric properties of these ceramics were systematically investigated. The impedance spectra were verified in the range from 1 Hz to 10 MHz at room temperature. The phase of the ceramics was found to primarily consist of wollastonite (CaSiO3), along with minor phases of γ-dicalcium silicate (Ca2SiO4) and quartz (SiO2). The sample with a cullet content of 55wt% possessed the optimum wollastonite structure and exhibited good dielectric properties. An increase of the cullet content beyond 55wt% resulted in a structural change from wollastonite to dicalcium silicate, a decrease in dielectric constant, and an increase in dielectric loss. All experimental results suggested that these novel ceramics from waste are applicable for electronic devices.

SrFe12O19 based ceramics with ultra-low dielectric loss in the millimetre-wave band

NASA Astrophysics Data System (ADS)

Yu, Chuying; Zeng, Yang; Yang, Bin; Wylde, Richard; Donnan, Robert; Wu, Jiyue; Xu, Jie; Gao, Feng; Abrahams, Isaac; Reece, Mike; Yan, Haixue

2018-04-01

Non-reciprocal devices such as isolators and circulators, based mainly on ferromagnetic materials, require extremely low dielectric loss in order for strict power-link budgets to be met for millimetre (mm)-wave and terahertz (THz) systems. The dielectric loss of commercial SrFe12O19 hexaferrite was significantly reduced to below 0.002 in the 75-170 GHz band by thermal annealing. While the overall concentration of Fe2+ and oxygen vacancy defects is relatively low in the solid, their concentration at the surface is significantly higher, allowing for a surface sensitive technique such as XPS to monitor the Fe3+/Fe2+ redox reaction. Oxidation of Fe2+ and a decrease in oxygen vacancies are found at the surface on annealing, which are reflected in the bulk sample by a small change in the unit cell volume. The significant decrease in the dielectric loss property can be attributed to the decreased concentration of charged defects such as Fe2+ and oxygen vacancies through the annealing process, which demonstrated that thermal annealing could be effective in improving the dielectric performance of ferromagnetic materials for various applications.

Laser-induced damage threshold measurements of optical dielectric coatings at lambda = 1.06 micron

NASA Astrophysics Data System (ADS)

Milev, I. Ia.; Dimov, S. S.; Terziev, D. V.; Iordanova, J. I.; Todorova, L. B.; Gelkova, A. B.

1991-10-01

The laser-induced damage thresholds for lambda = 1.06 micron of commercially available dielectric optical coatings, both antireflective and high reflectance, have been determined. The dependence of the optical coatings stability on design and selection of materials has been investigated. An improvement of the coatings durability by using nonquarterwave layers in addition to the basic design of the mirrors has been obtained. The choice of the coating materials is also discussed.

Full spectrum optical safeguard

DOEpatents

Ackerman, Mark R.

2008-12-02

An optical safeguard device with two linear variable Fabry-Perot filters aligned relative to a light source with at least one of the filters having a nonlinear dielectric constant material such that, when a light source produces a sufficiently high intensity light, the light alters the characteristics of the nonlinear dielectric constant material to reduce the intensity of light impacting a connected optical sensor. The device can be incorporated into an imaging system on a moving platform, such as an aircraft or satellite.

Exploration of BEOL line-space patterning options at 12 nm half-pitch and below

NASA Astrophysics Data System (ADS)

Decoster, S.; Lazzarino, F.; Petersen Barbosa Lima, L.; Li, W.; Versluijs, J.; Halder, S.; Mallik, A.; Murdoch, G.

2018-03-01

While the semiconductor industry is almost ready for high-volume manufacturing of the 7 nm technology node, research centers are defining and troubleshooting the patterning options for the 5 nm technology node (N5) and below. The target dimension for imec's N5 BEOL applications is 20-24 nm Metal Pitch (MP), which requires Self-Aligned multiple (Double/Quadruple/Octuple) Patterning approaches (SAxP) in combination with EUV or immersion lithography at 193 nm. There are numerous technical challenges to enable gratings at the hard mask level such as good uniformity across wafer, low line edge/width roughness (LER/LWR), large process window, and all of this at low cost. An even greater challenge is to transfer these gratings into the dielectric material at such critical dimensions, where increased line edge roughness, line wiggling and even pattern collapse can be expected for materials with small mechanical stability such as highly porous low-k dielectrics. In this work we first compare three different patterning options for 12 nm half-pitch gratings at the hard mask level: EUV-based SADP and 193i-based SAQP and SAOP. This comparison will be based on process window, line edge/width roughness and cost. Next, the transfer of 12 nm line/space gratings in the dielectric material is discussed and presented. The LER of the dielectric lines is investigated as a function of the dielectric material, the trench depth, and the stress in the sacrificial hard mask. Finally, we elaborate on the different options to enable scaling down from 24 nm MP to 16 nm MP, and demonstrate 8 nm line/space gratings with 193i-based SAOP.

Dielectric properties of biomass and biochar mixtures for bioenergy applications

USDA-ARS?s Scientific Manuscript database

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

The contribution of 180° domain wall motion to dielectric properties quantified from in situ X-ray diffraction

DOE PAGES

Fancher, C. M.; Brewer, S.; Chung, C. C.; ...

2016-12-27

Here, the contribution of 180° domain wall motion to polarization and dielectric properties of ferroelectric materials has yet to be determined experimentally. In this paper, an approach for estimating the extent of (180°) domain reversal during application of electric fields is presented. We demonstrate this method by determining the contribution of domain reversal to polarization in soft lead zirconate titanate during application of strong electric fields. At the maximum applied field, domain reversal was determined to account for >80% of the measured macroscopic polarization. We also apply the method to quantify the contribution of domain reversal to the weak-field dielectricmore » permittivity of BaTiO 3. The results of this analysis determined that domain reversal accounts for up to ~70% of the macroscopic dielectric permittivity in BaTiO 3. These results demonstrate the predominance of domain reversal to high and low-field dielectric response in ferroelectric polycrystalline materials.« less

High temperature dielectric properties of Apical, Kapton, Peek, Teflon AF, and Upilex polymers

NASA Technical Reports Server (NTRS)

Hammoud, A. N.; Baumann, E. D.; Overton, E.; Myers, I. T.; Suthar, J. L.; Khachen, W.; Laghari, J. R.

1992-01-01

Reliable lightweight systems capable of providing electrical power at the magawatt level are a requirement for future manned space exploration missions. This can be achieved by the development of high temperature insulating materials which are not only capable of surviving the hostile space environment but can contribute to reducing the mass and weight of the heat rejection system. In this work, Apical, Upilex, Kapton, Teflon AF, and Peek polymers are characterized for AC and DC dielectric breakdown in air and in silicone oil at temperatures up to 250 C. The materials are also tested in terms of their dielectric constant and dissipation factor at high temperatures with an electrical stress of 60 Hz, 200 V/mil present. The effects of thermal aging on the properties of the films are determined after 15 hours of exposure to 200 and 250 C, each. The results obtained are discussed and conclusions are made concerning the suitability of these dielectrics for use in capacitors and cable insulations in high temperature environments.

Low-loss Ca{sub 5-x}Sr{sub x}A{sub 2}TiO{sub 12} [A=Nb,Ta] ceramics: Microwave dielectric properties and vibrational spectroscopic analysis

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

Bijumon, Pazhoor Varghese; Sebastian, Mailadil Thomas; Dias, Anderson

2005-05-15

Complex perovskite-type Ca{sub 5-x}Sr{sub x}A{sub 2}TiO{sub 12} [A=Nb,Ta] (0{<=}x{<=}5) ceramics were prepared by conventional solid-state ceramic route. The crystal structure, microwave dielectric properties, and vibrational spectroscopic characteristics of these materials are reported. The structure and microstructure were investigated by x-ray diffraction and scanning electron microscopy techniques. The microwave dielectric properties were measured in the 3-5-GHz frequency range by the resonance method. Structural evolutions from orthorhombic to an averaged pseudocubic phase, with associated changes in dielectric properties, were observed as a function of composition. The structure-property relationships in these ceramics were established using Raman and Fourier transform infrared spectroscopic techniques. Ramanmore » analysis showed characteristic bands of ordered perovskite materials, with variation in both intensity and frequency as a function of composition.« less

Methods and apparatus for vertical coupling from dielectric waveguides

DOEpatents

Yaacobi, Ami; Cordova, Brad Gilbert

2014-06-17

A frequency-chirped nano-antenna provides efficient sub-wavelength vertical emission from a dielectric waveguide. In one example, this nano-antenna includes a set of plasmonic dipoles on the opposite side of a SiYV.sub.4 waveguide from a ground plane. The resulting structure, which is less than half a wavelength long, emits a broadband beam (e.g., >300 nm) that can be coupled into an optical fiber. In some embodiments, a diffractive optical element with unevenly shaped regions of high- and low-index dielectric material collimates the broadband beam for higher coupling efficiency. In some cases, a negative lens element between the nano-antenna and the diffractive optical element accelerates the emitted beam's divergence (and improves coupling efficiency), allowing for more compact packaging. Like the diffractive optical element, the negative lens element includes unevenly shaped regions of high- and low-index dielectric material that can be designed to compensate for aberrations in the beam emitted by the nano-antenna.

Terahertz dielectric response of photoexcited carriers in Si revealed via single-shot optical-pump and terahertz-probe spectroscopy

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

Minami, Yasuo; Horiuchi, Kohei; Masuda, Kaisei

We have demonstrated accurate observations of terahertz (THz) dielectric response due to photoexcited carriers in a Si plate via single-shot optical-pump and THz-probe spectroscopy. In contrast to conventional THz time-domain spectroscopy, this spectroscopic technique allows single-shot detection of the THz response of materials at a given delay time between the pump and THz pulses, thereby sufficiently extending the time interval between the pump pulses. As a result, we can accurately measure the dielectric properties of materials, while avoiding artifacts in the response caused by the accumulation of long-lived photoexcited carriers. Using our single-shot scheme, the transmittance of a Si platemore » was measured in the range of 0.5–2.5 THz with different pump fluences. Based on a Drude model analysis, the optically induced complex dielectric constant, plasma frequency, and damping rate in the THz region were quantitatively evaluated.« less

High temperature dielectric properties of Apical, Kapton, Peek, Teflon AF, and Upilex polymers

NASA Astrophysics Data System (ADS)

Hammoud, A. N.; Baumann, E. D.; Overton, E.; Myers, I. T.; Suthar, J. L.; Khachen, W.; Laghari, J. R.

1992-06-01

Reliable lightweight systems capable of providing electrical power at the magawatt level are a requirement for future manned space exploration missions. This can be achieved by the development of high temperature insulating materials which are not only capable of surviving the hostile space environment but can contribute to reducing the mass and weight of the heat rejection system. In this work, Apical, Upilex, Kapton, Teflon AF, and Peek polymers are characterized for AC and DC dielectric breakdown in air and in silicone oil at temperatures up to 250 C. The materials are also tested in terms of their dielectric constant and dissipation factor at high temperatures with an electrical stress of 60 Hz, 200 V/mil present. The effects of thermal aging on the properties of the films are determined after 15 hours of exposure to 200 and 250 C, each. The results obtained are discussed and conclusions are made concerning the suitability of these dielectrics for use in capacitors and cable insulations in high temperature environments.

Supercapacitors: Ferroelectric Polymer-Ceramic Nanoparticle Composite Films for Use in the Capacitive Storage of Electrical Energy

NASA Astrophysics Data System (ADS)

Parsons, Dana; Pierce, Andrew; Porter, Tim; Dillingham, Randy; Cornelison, David

2010-03-01

Most new alternative energy solutions including wind and solar power, will require short term energy storage for widespread implementation. One means of storage would be the use of capacitors owing to their rapid delivery of power and longevity compared to chemical batteries. Capacitor materials exhibiting high dielectric permittivity and breakdown strength, as well as light weight and environmental safety are most desirable. Recently, new classes of capacitor dielectric materials, consisting of ferroelectric polymer matrices containing ceramic nanoparticles have attracted renewed interest due to their high potential energy storage, charge and discharge properties and lightweight. In this study, polyvinylidene flouride (PVDF) thin films containing nanoparticles of the ceramic titanium dioxide created using a physical vapor deposition process, are analyzed for use as dielectrics for a supercapacitor. Measured results of the film parameters including dielectric properties and breakdown voltages will be presented. These parameters will be analyzed with respect to film characteristics such as, dispersion of the ceramic particles, thickness of the films and composition ratios.

Recent patents on Cu/low-k dielectrics interconnects in integrated circuits.

PubMed

Jiang, Qing; Zhu, Yong F; Zhao, Ming

2007-01-01

In past decades, the development of microelectronics has moved along with constant speed of scaling to maximize transistor density as driven by the need for electrical and functional performance. For further development, the propagation velocity of electromagnetic waves becomes increasingly important due to their unyielding constraints on interconnect delay. To minimize it, it was forced to the introduction of the Cu/low-k dielectric interconnects to very large scale integrated circuits (VLSI) where k denotes the dielectric constant. In addition, reliable barrier structures, which are the thinnest part among the device parts to maximize space availability for the actual Cu IWs, are required to prevent penetration of different materials. In light of the above statements, this review will focus recent patents and some studies on Cu interconnects including Cu interconnect wires, low-k dielectrics and related barrier materials as well manufacturing techniques in VLSI, which are one of the most essential concerns in microelectronic industry and decides the further development of VLSI. In addition, possible future development in this field is considered.

Effect of gamma radiation on dielectric and mechanical properties of modified fluoroplastic PTFE

NASA Astrophysics Data System (ADS)

Romanov, Boris; Kostromin, Valeriy; Bedenko, Sergey; Knyshev, Vladimir; Mukhnurov, Ilya; Matias, Rodrigo Roman

2018-03-01

The influence of gamma radiation on dielectric and mechanical characteristics of modified fluoroplast PTFE-4 MBK is considered in this paper. The material was exposed to Gamma-ray source GU-200 (Joint-stock company «Research Institute of Instruments», Lytkarino, Russia). The results of the research have shown that the relative permittivity and the tangent of the dielectric loss angle of PTFE-4 MBK samples at doses 4.105-1.106 Gy monotonically increase by 2.9 and 9.4%, respectively, compared to un-exposed material. The research of the mechanical properties of PTFE-4 MBK showed a maximum stress of up to 13.8 MPa and a maximum strain of 252% at doses of 8.104 Gy. It has been demonstrated that modified PTFE-4 MBK has good dielectric characteristics and withstanding high mechanical stress. We propose to use the results of the research for choosing cables and wiring location used in nuclear and space industry.

Advanced Capacitor with SiC for High Temperature Applications

NASA Astrophysics Data System (ADS)

Tsao, B. H.; Ramalingam, M. L.; Bhattacharya, R. S.; Carr, Sandra Fries

1994-07-01

An advanced capacitor using SiC as the dielectric material has been developed for high temperature, high power, and high density electronic components for aircraft and aerospace application. The conventional capacitor consists of a large number of metallized polysulfone films that are arranged in parallel and enclosed in a sealed metal case. However, problems with electrical failure, thermal failure, and dielectric flow were experienced by Air Force suppliers for the component and subsystem for lack of suitable properties of the dielectric material. The high breakdown electrical field, high thermal conductivity, and high temperature operational resistance of SiC compared to similar properties of the conventional ceramic and polymer capacitor would make it a better choice for a high temperature, and high power capacitor. The quality of the SiC film was evaluated. The electrical parameters, such as the capacitance, dissipation factor, equivalent series resistance, and dielectric withstand voltage, were evaluated. The prototypical capacitors are currently being fabricated using SiC film.

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

NASA Astrophysics Data System (ADS)

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

2010-02-01

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.

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

NASA Astrophysics Data System (ADS)

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

2016-10-01

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

Optically controlled dielectric properties of single-walled carbon nanotubes for terahertz wave applications.

PubMed

Smirnov, Serguei; Anoshkin, Ilya V; Demchenko, Petr; Gomon, Daniel; Lioubtchenko, Dmitri V; Khodzitsky, Mikhail; Oberhammer, Joachim

2018-06-21

Materials with tunable dielectric properties are valuable for a wide range of electronic devices, but are often lossy at terahertz frequencies. Here we experimentally report the tuning of the dielectric properties of single-walled carbon nanotubes under light illumination. The effect is demonstrated by measurements of impedance variations at low frequency as well as complex dielectric constant variations in the wide frequency range of 0.1-1 THz by time domain spectroscopy. We show that the dielectric constant is significantly modified for varying light intensities. The effect is also practically applied to phase shifters based on dielectric rod waveguides, loaded with carbon nanotube layers. The carbon nanotubes are used as tunable impedance surface controlled by light illumination, in the frequency range of 75-500 GHz. These results suggest that the effect of dielectric constant tuning with light, accompanied by low transmission losses of the carbon nanotube layer in such an ultra-wide band, may open up new directions for the design and fabrication of novel Terahertz and optoelectronic devices.

Dielectric and modulus analysis of the photoabsorber Cu2SnS3

NASA Astrophysics Data System (ADS)

Lahlali, S.; Essaleh, L.; Belaqziz, M.; Chehouani, H.; Alimoussa, A.; Djessas, K.; Viallet, B.; Gauffier, J. L.; Cayez, S.

2017-12-01

Dielectric properties of the ternary semiconductor compound Cu2SnS3 is studied for the first time in the high temperature range from 300 °C to 440 °C with the frequency range 1 kHz to 1 MHz. The dielectric constant ε ‧ and dielectric loss tan (δ) were observed to increase with temperature and decrease rapidly with frequency to remains constant at high frequencies. The variation of the dielectric loss Ln (ε ") with L n (ω) was found to follow the empirical law, ε " = B ω m (T). The dielectric data were analyzed using complex electrical modulus M* at various temperatures. The activation energy responsible for the relaxation is estimated from the analysis of the modulus spectra. The value of the hopping barrier potential is estimated from the dielectric loss and compared with the value previously obtained from ac-conductivity. These results are critical for understanding the behavior of based polycrystalline family of Cu2SnS3 for absorber materials in solar-cells.

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

NASA Astrophysics Data System (ADS)

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

2015-01-01

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

Aromatic Polythiourea Dielectrics with High Energy Density, High Breakdown Strength, and Low Dielectric Loss

NASA Astrophysics Data System (ADS)

Wu, Shan; Burlingame, Quinn; Lin, Minren; Zhang, Qiming

2013-03-01

There is an increasing demand on dielectric materials with high electric energy density and low loss for a broad range of applications in modern electronics and electrical power systems such as hybrid electric vehicles (HEV), medical defibrillators, filters, and switched-mode power supplies. One major challenge in developing dielectric polymers is how to achieve high energy density Ue while maintaining low dielectric loss, even at very high-applied electric fields. Here we show that amorphous polar-polymers with very low impurity concentration can be promising for realizing such a dielectric polymer. Polar-polymer with high dipole moment and weak dipole coupling can provide relatively high dielectric constant for high Ue, eliminate polarization and conduction losses due to weak dipolar coupling and strong polar-scattering to charge carriers. Indeed, an aromatic polythiourea thin film can maintain low loss to high fields (>1 GV/m) with a high Ue (~ 24 J/cm3) , which is very attractive for energy storage capacitors.

Photonic crystals, amorphous materials, and quasicrystals

PubMed Central

Edagawa, Keiichi

2014-01-01

Photonic crystals consist of artificial periodic structures of dielectrics, which have attracted much attention because of their wide range of potential applications in the field of optics. We may also fabricate artificial amorphous or quasicrystalline structures of dielectrics, i.e. photonic amorphous materials or photonic quasicrystals. So far, both theoretical and experimental studies have been conducted to reveal the characteristic features of their optical properties, as compared with those of conventional photonic crystals. In this article, we review these studies and discuss various aspects of photonic amorphous materials and photonic quasicrystals, including photonic band gap formation, light propagation properties, and characteristic photonic states. PMID:27877676

Photonic crystals, amorphous materials, and quasicrystals.

PubMed

Edagawa, Keiichi

2014-06-01

Photonic crystals consist of artificial periodic structures of dielectrics, which have attracted much attention because of their wide range of potential applications in the field of optics. We may also fabricate artificial amorphous or quasicrystalline structures of dielectrics, i.e. photonic amorphous materials or photonic quasicrystals. So far, both theoretical and experimental studies have been conducted to reveal the characteristic features of their optical properties, as compared with those of conventional photonic crystals. In this article, we review these studies and discuss various aspects of photonic amorphous materials and photonic quasicrystals, including photonic band gap formation, light propagation properties, and characteristic photonic states.

Low-temperature dielectric behavior of Nb{sub 2}O{sub 5}-SiO{sub 2} solid solutions.

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

Choosuwan, H.; Guo, R.; Bhalla, A. S.

2003-03-01

Dielectric properties of Nb{sub 2}O{sub 5}(0.92):SiO{sub 2}(0.08) ceramic were measured in the temperature range of 10-300 K by the cryostat system. Frequency-dependent dielectric loss suggests the relaxation behavior of this material. The relaxation mechanism was analyzed by the Arrhenius relationship and the Cole-Cole plot. Calculated distribution of relaxation time reveals deviation from the pure Debye relaxation.

Observation of backscattering-immune chiral electromagnetic modes without time reversal breaking.

PubMed

Chen, Wen-Jie; Hang, Zhi Hong; Dong, Jian-Wen; Xiao, Xiao; Wang, He-Zhou; Chan, C T

2011-07-08

A strategy is proposed to realize robust transport in a time reversal invariant photonic system. Using numerical simulation and a microwave experiment, we demonstrate that a chiral guided mode in the channel of a three-dimensional dielectric layer-by-layer photonic crystal is immune to the scattering of a square patch of metal or dielectric inserted to block the channel. The chirality based robust transport can be realized in nonmagnetic dielectric materials without any external field.

Structural, Dielectric, and Electrical Properties of Bi1- x Pb x Fe1- x (Zr0.5Ti0.5) x O3

NASA Astrophysics Data System (ADS)

Panda, Niranjan; Pattanayak, Samita; Choudhary, R. N. P.

2015-12-01

Polycrystalline samples of Bi1- x Pb x Fe1- x (Zr0.5Ti0.5) x O3 (BPFZTO) with x = 0.0, 0.2, 0.3, and 0.4 were prepared by high-temperature solid-state reaction. Preliminary structural analysis of calcined powders of the materials by use of x-ray powder diffraction confirmed formation of single-phase systems with the tetragonal structure. Room-temperature scanning electron micrographs of the samples revealed uniform distribution of grains of low porosity and different dimensions on the surface of the samples. The frequency-temperature dependence of dielectric and electric properties was studied by use of dielectric and complex impedance spectroscopy over a wide range of frequency (1 kHz to 1 MHz) at different temperatures (25-500°C). The dielectric constant of BiFeO3 (BFO) was enhanced by substitution with Pb(Zr0.5Ti0.5)O3 (PZT) whereas the dielectric loss of the BPFZTO compounds decreased with increasing PZT content. A significant contribution of both grains and grain boundaries to the electrical response of the materials was observed. The frequency-dependence of the ac conductivity of BPFZTO followed Jonscher's power law. Negative temperature coefficient of resistance behavior was observed for all the BPFZTO samples. Conductivity by thermally excited charge carriers and oxygen vacancies in the materials was believed to be of the Arrhenius-type.

Synthesis and characterization of (Bi{sub 0.5}Ba{sub 0.5}) (Fe{sub 0.5}Ti{sub 0.5}) O{sub 3} ceramic

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

Parida, B.N., E-mail: bichitra_mama@rediffmail.com; Das, Piyush R., E-mail: prdas63@gmail.com; Padhee, R.

2015-01-15

Graphical abstract: Temperature variation of (a) dielectric constant (b) dielectric loss of the sample. - Highlights: • The high values of dielectric permittivity and low value of tangent loss. • It used for microwave applications. • The impedance and dielectric relaxation in the material is non exponential and non Debye-type. • Its ac conductivity obeys Jonscher universal power law. - Abstract: The polycrystalline sample of (Bi{sub 0.5}Ba{sub 0.5}) (Fe{sub 0.5}Ti{sub 0.5}) O{sub 3} (BF–BT) was prepared by a standard mixed oxide method. Analysis of room temperature XRD pattern and Raman/FTIR spectra of the compound does not exhibit any change inmore » its crystal structure of BaTiO{sub 3} on addition of BiFeO{sub 3} in equal ratio. The surface morphology of the gold-plated sintered pellet sample recorded by SEM (scanning electron microscope) exhibits a uniform distribution of grains with less porosity. Detailed studies of nature and quantity of variation of dielectric constant, tangent loss, and polarization with temperature and frequency indicate the existence of ferroelectric phase transition at high-temperature. There is a low-temperature anti-ferromagnetic phase transition below 375 °C in the material. Detailed studies of electrical properties (impedance, modulus, etc.) of the material confirmed a strong correlation between micro-structure and properties.« less

Electrical conductivity, dielectric response and space charge dynamics of an electroactive polymer with and without nanofiller reinforcement

NASA Astrophysics Data System (ADS)

Kochetov, R.; Tsekmes, I. A.; Morshuis, P. H. F.

2015-07-01

Electroactive polymers have gained considerable attention over the last 20 years for exhibiting a large displacement in response to electrical stimulation. The promising fields of application include wave energy converters, muscle-like actuators, sensors, robotics, and biomimetics. For an electrical engineer, electroactive polymers can be seen as a dielectric elastomer film or a compliant capacitor with a highly deformable elastomeric medium. If the elastomer is pre-stretched and pre-charged, a reduction of the tensile force lets the elastomer revert to its original form and increases the electrical potential. The light weight of electroactive polymers, low cost, high intrinsic breakdown strength, cyclical way of operation, reliable performance, and high efficiency can be exploited to utilize the elastomeric material as a transducer. The energy storage for a linear dielectric polymer is determined by its relative permittivity and the applied electric field. The latter is limited by the dielectric breakdown strength of the material. Therefore, to generate a high energy density of a flexible capacitor, the film must be used at the voltage level close to the material’s breakdown or inorganic particles with high dielectric permittivity which can be introduced into the polymer matrix. In the present study, silicone-titania elastomer nanocomposites were produced and the influence of nanoparticles on the macroscopic dielectric properties of the neat elastomer including space charge dynamics, complex permittivity, and electrical conductivity, were investigated.

Studies on the structural, optical and dielectric properties of samarium coordinated with salicylic acid single crystal

NASA Astrophysics Data System (ADS)

Singh, Harjinder; Slathia, Goldy; Gupta, Rashmi; Bamzai, K. K.

2018-04-01

Samarium coordinated with salicylic acid was successfully grown as a single crystal by low temperature solution technique using mixed solvent of methanol and water in equal ratio. Structural characterization was carried out by single crystal X-ray diffraction analysis and it crystallizes in centrosymmetric space group P121/c1. FTIR and UV-Vis-NIR spectroscopy confirmed the compound formation and help to determine the mode of binding of the ligand to the rare earth-metal ion. Dielectric constant and dielectric loss have been measured over the frequency range 100 Hz - 30MHz. The decrease in dielectric constant with increases in frequency is due to the transition from interfacial polarization to dipolar polarization. The small value of dielectric constant at higher frequency ensures that the crystal is good candidate for NLO devices. Dielectric loss represents the resistive nature of the material.

Use of a hard mask for formation of gate and dielectric via nanofilament field emission devices

DOEpatents

Morse, Jeffrey D.; Contolini, Robert J.

2001-01-01

A process for fabricating a nanofilament field emission device in which a via in a dielectric layer is self-aligned to gate metal via structure located on top of the dielectric layer. By the use of a hard mask layer located on top of the gate metal layer, inert to the etch chemistry for the gate metal layer, and in which a via is formed by the pattern from etched nuclear tracks in a trackable material, a via is formed by the hard mask will eliminate any erosion of the gate metal layer during the dielectric via etch. Also, the hard mask layer will protect the gate metal layer while the gate structure is etched back from the edge of the dielectric via, if such is desired. This method provides more tolerance for the electroplating of a nanofilament in the dielectric via and sharpening of the nanofilament.

Giant optical field enhancement in multi-dielectric stacks by photon scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Ndiaye, C.; Zerrad, M.; Lereu, A. L.; Roche, R.; Dumas, Ph.; Lemarchand, F.; Amra, C.

2013-09-01

Dielectric optical thin films, as opposed to metallic, have been very sparsely explored as good candidates for absorption-based optical field enhancement. In such materials, the low imaginary part of the refractive index implies that absorption processes are usually not predominant. This leads to dielectric-based optical resonances mainly via waveguiding modes. We show here that when properly designed, a multi-layered dielectric thin films stack can give rise to optical resonances linked to total absorption. We report here, on such dielectric stack designed to possess a theoretical optical field enhancement above 1000. Using photon scanning tunneling microscopy, we experimentally evaluate the resulting field enhancement of the stack as well as the associated penetration depth. We thus demonstrate the capability of multi-dielectric stacks in generating giant optical field with tunable penetration depth (down to few dozens of nm).

Broadband high-efficiency dielectric metasurfaces for the visible spectrum

PubMed Central

Devlin, Robert C.; Khorasaninejad, Mohammadreza; Chen, Wei Ting; Oh, Jaewon; Capasso, Federico

2016-01-01

Metasurfaces are planar optical elements that hold promise for overcoming the limitations of refractive and conventional diffractive optics. Original dielectric metasurfaces are limited to transparency windows at infrared wavelengths because of significant optical absorption and loss at visible wavelengths. Thus, it is critical that new materials and nanofabrication techniques be developed to extend dielectric metasurfaces across the visible spectrum and to enable applications such as high numerical aperture lenses, color holograms, and wearable optics. Here, we demonstrate high performance dielectric metasurfaces in the form of holograms for red, green, and blue wavelengths with record absolute efficiency (>78%). We use atomic layer deposition of amorphous titanium dioxide with surface roughness less than 1 nm and negligible optical loss. We use a process for fabricating dielectric metasurfaces that allows us to produce anisotropic, subwavelength-spaced dielectric nanostructures with shape birefringence. This process is capable of realizing any high-efficiency metasurface optical element, e.g., metalenses and axicons. PMID:27601634

Core-shell structured polystyrene/BaTiO3 hybrid nanodielectrics prepared by in situ RAFT polymerization: a route to high dielectric constant and low loss materials with weak frequency dependence.

PubMed

Yang, Ke; Huang, Xingyi; Xie, Liyuan; Wu, Chao; Jiang, Pingkai; Tanaka, Toshikatsu

2012-11-23

A novel route to prepare core-shell structured nanocomposites with excellent dielectric performance is reported. This approach involves the grafting of polystyrene (PS) from the surface of BaTiO(3) by an in situ RAFT polymerization. The core-shell structured PS/BaTiO(3) nanocomposites not only show significantly increased dielectric constant and very low dielectric loss, but also have a weak frequency dependence of dielectric properties over a wide range of frequencies. In addition, the dielectric constant of the nanocomposites can also be easily tuned by varying the thickness of the PS shell. Our method is very promising for preparing high-performance nanocomposites used in energy-storage devices. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Defects in codoped NiO with gigantic dielectric response

NASA Astrophysics Data System (ADS)

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.

Experimental realization of a terahertz all-dielectric metasurface absorber.

PubMed

Liu, Xinyu; Fan, Kebin; Shadrivov, Ilya V; Padilla, Willie J

2017-01-09

Metamaterial absorbers consisting of metal, metal-dielectric, or dielectric materials have been realized across much of the electromagnetic spectrum and have demonstrated novel properties and applications. However, most absorbers utilize metals and thus are limited in applicability due to their low melting point, high Ohmic loss and high thermal conductivity. Other approaches rely on large dielectric structures and / or a supporting dielectric substrate as a loss mechanism, thereby realizing large absorption volumes. Here we present a terahertz (THz) all dielectric metasurface absorber based on hybrid dielectric waveguide resonances. We tune the metasurface geometry in order to overlap electric and magnetic dipole resonances at the same frequency, thus achieving an experimental absorption of 97.5%. A simulated dielectric metasurface achieves a total absorption coefficient enhancement factor of FT=140, with a small absorption volume. Our experimental results are well described by theory and simulations and not limited to the THz range, but may be extended to microwave, infrared and optical frequencies. The concept of an all-dielectric metasurface absorber offers a new route for control of the emission and absorption of electromagnetic radiation from surfaces with potential applications in energy harvesting, imaging, and sensing.

Role of the dielectric for the charging dynamics of the dielectric/barrier interface in AlGaN/GaN based metal-insulator-semiconductor structures under forward gate bias stress

NASA Astrophysics Data System (ADS)

Lagger, P.; Steinschifter, P.; Reiner, M.; Stadtmüller, M.; Denifl, G.; Naumann, A.; Müller, J.; Wilde, L.; Sundqvist, J.; Pogany, D.; Ostermaier, C.

2014-07-01

The high density of defect states at the dielectric/III-N interface in GaN based metal-insulator-semiconductor structures causes tremendous threshold voltage drifts, ΔVth, under forward gate bias conditions. A comprehensive study on different dielectric materials, as well as varying dielectric thickness tD and barrier thickness tB, is performed using capacitance-voltage analysis. It is revealed that the density of trapped electrons, ΔNit, scales with the dielectric capacitance under spill-over conditions, i.e., the accumulation of a second electron channel at the dielectric/AlGaN barrier interface. Hence, the density of trapped electrons is defined by the charging of the dielectric capacitance. The scaling behavior of ΔNit is explained universally by the density of accumulated electrons at the dielectric/III-N interface under spill-over conditions. We conclude that the overall density of interface defects is higher than what can be electrically measured, due to limits set by dielectric breakdown. These findings have a significant impact on the correct interpretation of threshold voltage drift data and are of relevance for the development of normally off and normally on III-N/GaN high electron mobility transistors with gate insulation.

Dielectric spectroscopy on organic charge-transfer salts

NASA Astrophysics Data System (ADS)

Lunkenheimer, P.; Loidl, A.

2015-09-01

This topical review provides an overview of the dielectric properties of a variety of organic charge-transfer salts, based on both, data reported in literature and our own experimental results. Moreover, we discuss in detail the different processes that can contribute to the dielectric response of these materials. We concentrate on the family of the 1D (TMTTF)2 X systems and the 2D BEDT-TTF-based charge-transfer salts, which in recent years have attracted considerable interest due to their often intriguing dielectric properties. We will mainly focus on the occurrence of electronic ferroelectricity in these systems, which also includes examples of multiferroicity.

Dielectric spectroscopy on organic charge-transfer salts.

PubMed

Lunkenheimer, P; Loidl, A

2015-09-23

This topical review provides an overview of the dielectric properties of a variety of organic charge-transfer salts, based on both, data reported in literature and our own experimental results. Moreover, we discuss in detail the different processes that can contribute to the dielectric response of these materials. We concentrate on the family of the 1D (TMTTF)2 X systems and the 2D BEDT-TTF-based charge-transfer salts, which in recent years have attracted considerable interest due to their often intriguing dielectric properties. We will mainly focus on the occurrence of electronic ferroelectricity in these systems, which also includes examples of multiferroicity.

Novel techniques for optical sensor using single core multi-layer structures for electric field detection

NASA Astrophysics Data System (ADS)

Ali, Amir R.; Kamel, Mohamed A.

2017-05-01

This paper studies the effect of the electrostriction force on the single optical dielectric core coated with multi-layers based on whispering gallery mode (WGM). The sensing element is a dielectric core made of polymeric material coated with multi-layers having different dielectric and mechanical properties. The external electric field deforming the sensing element causing shifts in its WGM spectrum. The multi-layer structures will enhance the body and the pressure forces acting on the core of the sensing element. Due to the gradient on the dielectric permittivity; pressure forces at the interface between every two layers will be created. Also, the gradient on Young's modulus will affect the overall stiffness of the optical sensor. In turn the sensitivity of the optical sensor to the electric field will be increased when the materials of each layer selected properly. A mathematical model is used to test the effect for that multi-layer structures. Two layering techniques are considered to increase the sensor's sensitivity; (i) Pressure force enhancement technique; and (ii) Young's modulus reduction technique. In the first technique, Young's modulus is kept constant for all layers, while the dielectric permittivity is varying. In this technique the results will be affected by the value dielectric permittivity of the outer medium surrounding the cavity. If the medium's dielectric permittivity is greater than that of the cavity, then the ascending ordered layers of the cavity will yield the highest sensitivity (the core will have the smallest dielectric permittivity) to the applied electric field and vice versa. In the second technique, Young's modulus is varying along the layers, while the dielectric permittivity has a certain constant value per layer. On the other hand, the descending order will enhance the sensitivity in the second technique. Overall, results show the multi-layer cavity based on these techniques will enhance the sensitivity compared to the typical polymeric optical sensor.

Polarization ratio property and material classification method in passive millimeter wave polarimetric imaging

NASA Astrophysics Data System (ADS)

Cheng, Yayun; Qi, Bo; Liu, Siyuan; Hu, Fei; Gui, Liangqi; Peng, Xiaohui

2016-10-01

Polarimetric measurements can provide additional information as compared to unpolarized ones. In this paper, linear polarization ratio (LPR) is created to be a feature discriminator. The LPR properties of several materials are investigated using Fresnel theory. The theoretical results show that LPR is sensitive to the material type (metal or dielectric). Then a linear polarization ratio-based (LPR-based) method is presented to distinguish between metal and dielectric materials. In order to apply this method to practical applications, the optimal range of incident angle have been discussed. The typical outdoor experiments including various objects such as aluminum plate, grass, concrete, soil and wood, have been conducted to validate the presented classification method.

Dielectric Characterization of PCL-Based Thermoplastic Materials for Microwave Diagnostic and Therapeutic Applications

PubMed Central

Aguilar, Suzette M.; Shea, Jacob D.; Al-Joumayly, Mudar A.; Van Veen, Barry D.; Behdad, Nader; Hagness, Susan C.

2011-01-01

We propose the use of a polycaprolactone (PCL)-based thermoplastic mesh as a tissue-immobilization interface for microwave imaging and microwave hyperthermia treatment. An investigation of the dielectric properties of two PCL-based thermoplastic materials in the frequency range of 0.5 – 3.5 GHz is presented. The frequency-dependent dielectric constant and effective conductivity of the PCL-based thermoplastics are characterized using measurements of microstrip transmission lines fabricated on substrates comprised of the thermoplastic meshes. We also examine the impact of the presence of a PCL-based thermoplastic mesh on microwave breast imaging. We use a numerical test bed comprised of a previously reported three-dimensional anatomically realistic breast phantom and a multi-frequency microwave inverse scattering algorithm. We demonstrate that the PCL-based thermoplastic material and the assumed biocompatible medium of vegetable oil are sufficiently well matched such that the PCL layer may be neglected by the imaging solution without sacrificing imaging quality. Our results suggest that PCL-based thermoplastics are promising materials as tissue immobilization structures for microwave diagnostic and therapeutic applications. PMID:21622068

Characterization of Hard Piezoelectric Lead-Free Ceramics

PubMed Central

Zhang, Shujun; Lim, Jong Bong; Lee, Hyeong Jae; Shrout, Thomas R.

2010-01-01

K4CuNb8O23 doped K0.45Na0.55NbO3 (KNN-KCN) ferroelectric ceramics were found to exhibit asymmetrical polarization hysteresis loops, related to the development of an internal bias field. The internal bias field is believed to be the result of defect dipoles of acceptor ions and oxygen vacancies, which lead to piezoelectric “hardening” effect, by stabilizing and pinning of the domain wall motion. The dielectric loss for the hard lead-free piezoelectric ceramic was found to be 0.6%, with mechanical quality factors Q on the order of >1500. Furthermore, the piezoelectric properties were found to decrease and the coercive field increased, when compared with the undoped material, exhibiting a typical characteristic of “hard” behavior. The temperature usage range was limited by the polymorphic phase transition temperature, being 188°C. The full set of material constants was determined for the KNN-KCN materials. Compared with conventional hard PZT ceramics, the lead-free possessed lower dielectric and piezoelectric properties; however, comparable values of mechanical Q, dielectric loss, and coercive fields were obtained, making acceptor modified KNN based lead-free piezoelectric material promising for high-power applications, where lead-free materials are desirable. PMID:19686966

Simple model dielectric functions for insulators

NASA Astrophysics Data System (ADS)

Vos, Maarten; Grande, Pedro L.

2017-05-01

The Drude dielectric function is a simple way of describing the dielectric function of free electron materials, which have an uniform electron density, in a classical way. The Mermin dielectric function describes a free electron gas, but is based on quantum physics. More complex metals have varying electron densities and are often described by a sum of Drude dielectric functions, the weight of each function being taken proportional to the volume with the corresponding density. Here we describe a slight variation on the Drude dielectric functions that describes insulators in a semi-classical way and a form of the Levine-Louie dielectric function including a relaxation time that does the same within the framework of quantum physics. In the optical limit the semi-classical description of an insulator and the quantum physics description coincide, in the same way as the Drude and Mermin dielectric function coincide in the optical limit for metals. There is a simple relation between the coefficients used in the classical and quantum approaches, a relation that ensures that the obtained dielectric function corresponds to the right static refractive index. For water we give a comparison of the model dielectric function at non-zero momentum with inelastic X-ray measurements, both at relative small momenta and in the Compton limit. The Levine-Louie dielectric function including a relaxation time describes the spectra at small momentum quite well, but in the Compton limit there are significant deviations.

Nonintrinsic origin of the colossal dielectric constants in Ca Cu3 Ti4 O12

NASA Astrophysics Data System (ADS)

Lunkenheimer, P.; Fichtl, R.; Ebbinghaus, S. G.; Loidl, A.

2004-11-01

The dielectric properties of CaCu3Ti4O12 , a material showing colossal values of the dielectric constant, were investigated over a broad temperature and frequency range extending up to 1.3GHz . A detailed equivalent-circuit analysis of the results and two crucial experiments, employing different types of contacts and varying the sample thickness were performed. The results provide clear evidence that the apparently high values of the dielectric constant in CaCu3Ti4O12 are nonintrinsic and due to electrode polarization effects. The intrinsic properties of CaCu3Ti4O12 are characterized by charge transport via hopping of localized charge carriers and a relatively high dielectric constant of the order of 100.

Dielectric relaxation in epitaxial films of paraelectric-magnetic SrTiO3-SrMnO3 solid solution

NASA Astrophysics Data System (ADS)

Savinov, M.; Bovtun, V.; Tereshina-Chitrova, E.; Stupakov, A.; Dejneka, A.; Tyunina, M.

2018-01-01

Magneto-dielectric properties of (A2+)MnO3-type perovskites are attractive for applications and stimulate extensive studies of these materials. Here, the complex dielectric and magnetic responses are investigated as in epitaxial films of SrTi0.6Mn0.4O3, solid solution of paraelectric SrTiO3 and magnetic SrMnO3. The impedance and resonance measurements at frequencies of 10-2-1010 Hz and temperatures of 10-500 K reveal broad dielectric anomalies centered at 100-200 K, while the films are paramagnetic at all temperatures. Analysis shows polaronic electrical conductivity behind the observed behavior. Electron-phonon correlations, rather than spin-phonon correlations, are suggested to produce the apparent magneto-dielectric responses in many multiferroic manganites.

Multiferroic behavior in CdCr2X4(X=S,Se)

NASA Astrophysics Data System (ADS)

Hemberger, J.; Lunkenheimer, P.; Fichtl, R.; Weber, S.; Tsurkan, V.; Loidl, A.

2006-05-01

The recently discovered multiferroic material CdCr2S4 shows a coexistence of ferromagnetism and relaxor ferroelectricity together with a colossal magnetocapacitive effect. The complex dielectric permittivity of this compound and of the structurally related CdCr2Se4 was studied by means of broadband dielectric spectroscopy using different electrode materials. The observed magnetocapacitive coupling at the magnetic transition is driven by enormous changes of the relaxation dynamics induced by the development of magnetic order.

Scanning evanescent electro-magnetic microscope

DOEpatents

Xiang, Xiao-Dong; Gao, Chen; Schultz, Peter G.; Wei, Tao

2003-01-01

A novel scanning microscope is described that uses near-field evanescent electromagnetic waves to probe sample properties. The novel microscope is capable of high resolution imaging and quantitative measurements of the electrical properties of the sample. The inventive scanning evanescent wave electromagnetic microscope (SEMM) can map dielectric constant, tangent loss, conductivity, complex electrical impedance, and other electrical parameters of materials. The quantitative map corresponds to the imaged detail. The novel microscope can be used to measure electrical properties of both dielectric and electrically conducting materials.

Scanning evanescent electro-magnetic microscope

DOEpatents

Xiang, Xiao-Dong; Gao, Chen

2001-01-01

A novel scanning microscope is described that uses near-field evanescent electromagnetic waves to probe sample properties. The novel microscope is capable of high resolution imaging and quantitative measurements of the electrical properties of the sample. The inventive scanning evanescent wave electromagnetic microscope (SEMM) can map dielectric constant, tangent loss, conductivity, complex electrical impedance, and other electrical parameters of materials. The quantitative map corresponds to the imaged detail. The novel microscope can be used to measure electrical properties of both dielectric and electrically conducting materials.

Terahertz Mapping of Microstructure and Thickness Variations

NASA Technical Reports Server (NTRS)

Roth, Donald J.; Seebo, Jeffrey P.; Winfree, William P.

2010-01-01

A noncontact method has been devised for mapping or imaging spatial variations in the thickness and microstructure of a layer of a dielectric material. The method involves (1) placement of the dielectric material on a metal substrate, (2) through-the-thickness pulse-echo measurements by use of electromagnetic waves in the terahertz frequency range with a raster scan in a plane parallel to the substrate surface that do not require coupling of any kind, and (3) appropriate processing of the digitized measurement data.

Study of a Waveguide Antenna Implemented in Laminated Material

DTIC Science & Technology

2002-12-01

CRC had some experience with fabricating microwave circuits with laminated copper clad dielectric. There was bonding material (CLTE-P) that could be...PEC) and copper walls in Table 4. For all of the simulations, the physical parameters (width= 5.13 mm, height=3.40 mm, length=24.27 mm) and the... copper waveguide. As shown in Chapter 2, it is also possible to determine the losses from the conductor and dielectric (Equations 2.6 - 2.8) of a RWG

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

Summary Report of the Summer Conference DARPA-Materials Research Council Held in La Jolla, California on 10 July thru 4 August 1989

DTIC Science & Technology

1989-08-04

ceramic substrate and a multilayer thin film metal (copper) and polymer ( polyimide ) overlays. 73 The MCM technology was pioneered by IBM, which has made...packaging. The first is the use of polymeric dielectric layers such as polyimides . In fact, the current MCP’s 3 being developed for the DoD use... polyimide dielectrics. Nonetheless, much work remains to be done before these organic dielectrics can be regarded as Isatisfactory. Polyimides have a

Plasmonic Sensor Based on Dielectric Nanoprisms

NASA Astrophysics Data System (ADS)

Elshorbagy, Mahmoud H.; Cuadrado, Alexander; Alda, Javier

2017-11-01

A periodic array of extruded nanoprisms is proposed to generate surface plasmon resonances for sensing applications. Nanoprisms guide and funnel light towards the metal-dielectric interface where the dielectric acts as the medium under test. The system works under normal incidence conditions and is spectrally interrogated. The performance is better than the classical Kretschmann configurations, and the values of sensitivity and figure of merit are competitive with other plasmonic sensor technologies. The geometry and the choice of materials have been made taking into account applicable fabrication constraints.

Disorder-Enhanced Dielectric Response of Nanoscale and Mesoscopic Insulators

NASA Astrophysics Data System (ADS)

Onoda, Shigeki; Chern, Chyh-Hong; Murakami, Shuichi; Ogimoto, Yasushi; Nagaosa, Naoto

2006-12-01

Enhancement of the dielectric response of insulators by disorder is theoretically proposed, where the quantum interference of electronic waves through the nanoscale or mesoscopic system and its change due to external perturbations control the polarization. In the disordered case with all the states being localized, the resonant tunneling, which is topologically protected, plays a crucial role, and enhances the dielectric response by a factor 30 40 compared with the pure case. The realization of this idea with accessible materials or structures is also discussed.

Development of dielectric elastomer nanocomposites as stretchable actuating materials

NASA Astrophysics Data System (ADS)

Wang, Yu; Sun, L. Z.

2017-10-01

Dielectric elastomer nanocomposites (DENCs) filled with multi-walled carbon nanotubes are developed. The electromechanical responses of DENCs to applied electric fields are investigated through laser Doppler vibrometry. It is found that a small amount of carbon nanotube fillers can effectively enhance the electromechanical performance of DENCs. The enhanced electromechanical properties have shown not only that the desired thickness strain can be achieved with reduced required electric fields but also that significantly large thickness strain can be obtained with any electric fields compared to pristine dielectric elastomers.

Method for making surfactant-templated, high-porosity thin films

DOEpatents

Brinker, C. Jeffrey; Lu, Yunfeng; Fan, Hongyou

2001-01-01

An evaporation-induced self-assembly method to prepare a surfactant-templated thin film by mixing a silica sol, a surfactant, and a hydrophobic polymer and then evaporating a portion of the solvent during coating onto a substrate and then heating to form a liquid-phase, thin film material with a porosity greater than approximately 50 percent. The high porosity thin films can have dielectric constants less than 2 to be suitable for applications requiring low-dielectric constants. An interstitial compound can be added to the mixture, with the interstitial compound either covalently bonded to the pores or physically entrapped within the porous structure. The selection of the interstitial compound provides a means for developing thin films for applications including membranes, sensors, low dielectric constant films, photonic materials and optical hosts.

Magnetocapacitance without magnetism

PubMed Central

Parish, Meera M.

2014-01-01

A substantial magnetodielectric effect is often an indication of coupled magnetic and elastic order, such as is found in the multi-ferroics. However, it has recently been shown that magnetism is not necessary to produce either a magnetoresistance or a magnetocapacitance when the material is inhomogeneous. Here, we will investigate the characteristic magnetic-field-dependent dielectric response of such an inhomogeneous system using exact calculations and numerical simulations of conductor–dielectric composites. In particular, we will show that even simple conductor–dielectric layers exhibit a magneto-capacitance, and thus random bulk inhomogeneities are not a requirement for this effect. Indeed, this work essentially provides a natural generalization of the Maxwell–Wagner effect to finite magnetic field. We will also discuss how this phenomenon has already been observed experimentally in some materials. PMID:24421378

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

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

Precision capacitor has improved temperature and operational stability

NASA Technical Reports Server (NTRS)

Brookshier, W. K.; Lewis, R. N.

1967-01-01

Vacuum dielectric capacitor is fabricated from materials with very low temperature coefficients of expansion. This precision capacitor in the 1000-2000 picofarad range has a near-zero temperature coefficient of capacitance, eliminates ion chamber action caused by air ionization in the dielectric, and minimizes electromagnetic field charging effects.

Topological phase transformations and intrinsic size effects in ferroelectric nanoparticles

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

Mangeri, John; Espinal, Yomery; Jokisaari, Andrea M.

Here, composite materials comprised of ferroelectric nanoparticles in a dielectric matrix are being actively investigated for a variety of functional properties attractive for a wide range of novel electronic and energy harvesting devices. However, the dependence of these functionalities on shapes, sizes, orientation and mutual arrangement of ferroelectric particles is currently not fully understood. In this study, we utilize a time-dependent Ginzburg-Landau approach combined with coupled-physics finite-element-method based simulations to elucidate the behavior of polarization in isolated spherical PbTiO 3 or BaTiO 3 nanoparticles embedded in a dielectric medium, including air. The equilibrium polarization topology is strongly affected by particlemore » diameter, as well as the choice of inclusion and matrix materials, with monodomain, vortex-like and multidomain patterns emerging for various combinations of size and materials parameters. This leads to radically different polarization vs electric field responses, resulting in highly tunable size-dependent dielectric properties that should be possible to observe experimentally. Our calculations show that there is a critical particle size below which ferroelectricity vanishes. For the PbTiO 3 particle, this size is 2 and 3.4 nm, respectively, for high- and low-permittivity media. For the BaTiO 3 particle, it is ~3.6 nm regardless of the medium dielectric strength.« less