SEARCH · Search NASA

Results for “electric permittivity”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3

All sources NASA NTRS DOE OSTI

DOE OSTI2023

Lead-free Zr-doped ceria ceramics with low permittivity displaying giant electrostriction

Electrostrictors, materials developing mechanical strain proportional to the square of the applied electric field, present many advantages for mechanical actuation as they convert electrical energy into mechanical, but not vice versa. Both high relative permittivity and reliance on Pb as the key component in commercial electrostrictors pose serious practical and health problems. Here we describe a low relative permittivity (<250) ceramic, Zr x Ce 1-x O 2 (x < 0.2), that displays electromechanical properties rivaling those of the best performing electrostrictors: longitudinal electrostriction strain coefficient ~10 -16 m 2 /V 2 ; relaxation frequency ≈ a few kHz; and strain ≥0.02%. Combining X-ray absorption spectroscopy, atomic-level modeling and electromechanical measurements, here we show that electrostriction in Zr x Ce 1-x O 2 is enabled by elastic dipoles produced by anharmonic motion of the smaller isovalent dopant (Zr). Unlike the elastic dipoles in aliovalent doped ceria, which are present even in the absence of an applied elastic or electric field, the elastic dipoles in Zr x Ce 1-x O 2 are formed only under applied anisotropic field. The local descriptors of electrostrictive strain, namely, the cation size mismatch and dynamic anharmonicity, are sufficiently versatile to guide future searches in other polycrystalline solids.

36 MATERIALS SCIENCE↗

DOE OSTI2023

High field dielectric response in κ-Ga 2 O 3 films

κ-Ga 2 O 3 has been predicted to be a potential ferroelectric material. In this work, undoped Ga 2 O 3 films were grown by either plasma-enhanced atomic layer deposition (PEALD) or metal organic chemical vapor deposition (MOCVD) on platinized sapphire substrates. 50 nm thick PEALD films with a mixture of κ-Ga 2 O 3 and β-Ga 2 O 3 had a relative permittivity of ~27, a loss tangent below 2%, and high electrical resistivity up to ~1.5 MV/cm. 700 nm thick MOCVD films with predominantly the κ-Ga 2 O 3 phase had relative permittivities of ~18 and a loss tangent of 1% at 10 kHz. Neither film showed compelling evidence for ferroelectricity measured at fields up to 1.5 MV/cm, even after hundreds of cycles. Here, piezoresponse force microscopy measurements on bare κ-Ga 2 O 3 showed a finite piezoelectric response that could not be reoriented for electric fields up to 1.33 MV/cm.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Finite-size effects in lead scandium tantalate relaxor thin films

Large electromechanical effects in relaxor ferroelectrics are generally attributed to the collective response of an ensemble of correlated, nanometer-sized polar structures induced by chemical and charge disorder. Here, we study finite-size effects on such polar order (i.e., how it evolves when sample dimensions approach the polarization correlation length) in 7–70-nm-thick films of the relaxor ferroelectric PbSc 0.5 Ta 0.5 O 3 . Temperature-dependent polarization studies reveal a linear suppression of the polarization and nonlinearity associated with relaxor order as the film thickness decreases to ≈ 30 nm. Below this thickness, however, the suppression rapidly accelerates, and polarization is completely absent by film thicknesses of ≈ 7 nm, despite the continued observation of a broad peak in dielectric permittivity and frequency dispersion. Diffuse-scattering measurements reveal the diffuse-scattering symmetry, and analysis suggests the films have a polarization correlation length of ≈ 23 nm. Finally, taken together, it is apparent that reduction of sample size and the resulting distribution of polar structures drive suppression and eventual quenching of the electrical response of relaxors, which may be attributed to increasing dipole-dipole and dipole-interface interactions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

NASA NTRS1974

Electrical properties of sample 70215 - Low-frequency corrections

Dielectric permittivity, loss tangent, and direct current conductivity of solid sample 70215,14 were measured at temperatures ranging from 100 to 373 K and vacuums of .01 to .1 microtorr; alternating current measurements were made in the 30 Hz to 100 kHz frequency range. It is concluded that dc conductivity undergoes a three order-of-magnitude change between lunar day and lunar night. The assumption is made that strong k' increments at the lower frequencies are partially induced by electrode and dc conductivity effects. Corrections were applied to the experimental data; corrected results suggest relaxation processes occurring at frequencies below 1 kHz.

Alvarez, R.↗

NASA NTRS1989

Solutions of differential equations with regular coefficients by the methods of Richmond and Runge-Kutta

Numerical solutions of the differential equation which describe the electric field within an inhomogeneous layer of permittivity, upon which a perpendicularly-polarized plane wave is incident, are considered. Richmond's method and the Runge-Kutta method are compared for linear and exponential profiles of permittivities. These two approximate solutions are also compared with the exact solutions.

Cockrell, C. R.↗

NASA NTRS2012

Open Circuit Resonant (SansEC) Sensor for Composite Damage Detection and Diagnosis in Aircraft Lightning Environments

Composite materials are increasingly used in modern aircraft for reducing weight, improving fuel efficiency, and enhancing the overall design, performance, and manufacturability of airborne vehicles. Materials such as fiberglass reinforced composites (FRC) and carbon-fiber-reinforced polymers (CFRP) are being used to great advantage in airframes, wings, engine nacelles, turbine blades, fairings, fuselage and empennage structures, control surfaces and coverings. However, the potential damage from the direct and indirect effects of lightning strikes is of increased concern to aircraft designers and operators. When a lightning strike occurs, the points of attachment and detachment on the aircraft surface must be found by visual inspection, and then assessed for damage by maintenance personnel to ensure continued safe flight operations. In this paper, a new method and system for aircraft in-situ damage detection and diagnosis are presented. The method and system are based on open circuit (SansEC) sensor technology developed at NASA Langley Research Center. SansEC (Sans Electric Connection) sensor technology is a new technical framework for designing, powering, and interrogating sensors to detect damage in composite materials. Damage in composite material is generally associated with a localized change in material permittivity and/or conductivity. These changes are sensed using SansEC. Unique electrical signatures are used for damage detection and diagnosis. NASA LaRC has both experimentally and theoretically demonstrated that SansEC sensors can be effectively used for in-situ composite damage detection.

Wang, Chuantong↗

NASA NTRS1988

Material parameter determination from scattering measurements

The electrical, macroscopic performance of isotropic material can generally be described through their constitutive scalar parameters, permittivity and permeability which are symbolically represented by epsilon and mu, respectively. These parameters relate the electric and magnetic flux densities to the electric and magnetic fields through the following relationships: (1) D=epsilonE; and (2) B=muH. It is through these parameters that the interaction of electromagnetic waves with material can be quantized in terms of reflection and transmission coefficients, and propagation and attenuation factors.

Dominek, A.↗

DOE OSTI2021

Phase coexistence at the first-order Mott transition revealed by pressure-dependent dielectric spectroscopy of κ - (BEDT-TTF) 2 - Cu 2 (CN) 3

The dimer Mott insulator kappa - (BEDT-TTF) 2 - Cu 2 (CN) 3 can be tuned into metallic and superconducting states on applying pressure of 1.5 kbar and more. We have performed dielectric measurements (7.5 kHz to 5 MHz) on kappa - (BEDT-TTF) 2 - Cu 2 (CN) 3 single crystals as a function of temperature (down to T = 8 K) and pressure (up to p = 4.3 kbar). In addition to the relaxor-like dielectric behavior seen below 50 K at p = 0, that moves toward lower temperatures with pressure, a second peak emerges in ε 1 (T) around T = 15 K. When approaching the insulator-metal boundary, this peak diverges rapidly reaching ε 1 ≈ 10 5 . Our dynamical mean-field theory calculations substantiate that the dielectric catastrophe at the Mott transition is not caused by closing the energy gap, but due to the spatial coexistence of correlated metallic and insulating regions. We discuss the percolative nature of the first-order Mott insulator-to-metal transition in all details.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

NASA NTRS2021

Temperature and Frequency Dependent Electrical Properties of AVCOAT and Shuttle Tile Material

This technical memorandum presents the data and results from a series of tests performed on AVCOAT, charred AVCOAT, and different Shuttle Thermal Protection System (TPS) tile coatings to determine their electrical properties as a function of temperature and frequency. Initially, the samples were assumed to be insulators and the complex permittivities were measured from data collected by sandwiching each sample between two conductors to form a sandwich. However, the AVCOAT sample data showed that the material becomes conductive as it begins to char. To get an accurate conductivity reading on these charred samples, a four-point resistance probe was used to collect data. Overall, this testing showed that the virgin AVCOAT starts out as a material that is a good insulator but transitions to one with a conductivity on the order of 1860 S/m as it chars. The deeper layers of AVCOAT (un-charred) all exhibited a temperature and frequency dependence that is possibly indicative of a dielectric relaxation in the material. As the sample temperatures were increased, a knee appears in the real permittivity data sets below 1 kHz. Both the real permittivity and resistivity drop up to several orders of magnitude yet show that the material remains an insulator. The Shuttle High Temperature Reusable Surface Insulation (HRSI) tile coatings studied included Reac- tion Cured Glass (RCG), Aluminum Enhanced Thermal Barrier (AETB), and Toughened Unipiece Fibrous Insulation (TUFI). The purely glass fiber parts of the tile were removed leaving only the outer layers con- taining just the coating. The data collected shows that the RCG, AETB, and outermost layer of the TUFI have similar electrical properties. The real permittivity plots show that there appears to be a relaxation that shows up at frequencies below 1 kHz. The relaxation frequency increases with increasing temperature. Also, the real permittivity increases up to about a factor of four between room temperature and 650K. Likewise, the resistivity (related to the imaginary permittivity) decreases up to five orders of magnitude over the same temperature interval, but still remains an insulator. This data was collected to support a NASA Engineering and Safety Center (NESC) assessment team investigating the source of thermocouple anomalies in both Shuttle TPS material and AVCOAT used for on the Orion spacecraft for Exploration Flight Test 1 (EFT-1). The details of their findings will be documented in a separate report with this document serving as a reference.

Mark A Nurge↗

NASA NTRS1989

A moment method solution of a volume-surface integral equation using isoparametric elements and point matching

Three integral equations for TE (transverse electric) scattering by dielectric cylinders having large values of permittivity are examined. A moment-method solution of the volume-surface integral equation is developed employing isoparametric elements and point matching. The solution is shown to be more accurate and stable than the traditional solutions using pulse basis, particularly in the case of scatterers having large refractive indices.

Jin, Jian-Ming↗

NASA NTRS1985

Characteristic Impedance of a Wide Slot Line on Low Permittivity Substrates

Computed results on the characteristic impedance of wide slots etched on an electrically thin substrate of low dielectric constant epsilon sub r are presented. Results are given for epsilon sub r = 2.22, 3.0, 3.8 and 9.8. Comparison is shown for the characteristic impedance between the present calculations and those available in the literature for high-epsilon sub r substrates.

Janaswamy, R.↗

NASA NTRS1986

Characteristic impedance of a wide slot line on low permittivity substrates

Computed results on the characteristics impedance of wide slots etched on an electrically thin substrate of low dielectric constant epsilon sub r are presented. These results are used to help provide design data for slotlines. Curves are presented for epsilon sub r = 2.22, 3.0, 3.8, and 9.8. Comparison is shown for the characteristic impedance between the present calculations and those available in the literature for high-epsilon sub r substrates. Empirical formulas, based on least square curve fitting, are presented for the normalized slot wavelength lambda prime/lambda sub 0 and the characteristic impedance Z sub 0 over the range: 0.0015 is equal to or less than W/lambda sub 0 equal to or less than 1.0, 0.006 is equal to or less than d/lambda sub 0 equal to or less than 0.06, 2.22 is equal to or less than epsilon sub 0 equal to or less than 9.8.

Janaswamy, R.↗

NASA NTRS1986

Characteristic impedance of a wide slotline on low-permittivity substrates

Janaswamy, R.↗

DOE OSTI2021

Hybrid BaTiO 3 /SiN x /AlGaN/GaN lateral Schottky barrier diodes with low turn-on and high breakdown performance

In this Letter, we demonstrate hybrid GaN lateral Schottky barrier diodes with enhanced breakdown characteristics and a low turn-on voltage. These diodes incorporate a lateral Schottky barrier in combination with a high permittivity material beneath the field plate, enabling high average breakdown fields and a low turn-on voltage. Average electric fields up to 2.38 MV/cm were achieved for devices with an anode–cathode spacing of 4 μm, while maintaining with a turn-on voltage of 0.48 V. In contrast, SiN x /AlGaN/GaN control lateral Schottky diodes displayed an average breakdown field of ~0.7 MV/cm for devices with similar dimensions with a turn-on voltage of 0.46 V. The use of a high-permittivity dielectric can more effectively utilize the high breakdown fields in wide bandgap materials by proper management of the electric field. This demonstration provides an innovative way to integrate high-permittivity materials with GaN lateral devices for improved breakdown and resistance characteristics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Understanding the surface wave characteristics using 2D particle-in-cell simulation and deep neural network

Here, the characteristics of the surface waves along the interface between a plasma and a dielectric material have been investigated using kinetic particle-in-cell simulations. A microwave source of GHz frequency has been used to trigger the surface wave in the system. The outcome indicates that the surface wave gets excited along the interface of plasma and the dielectric tube and appears as light and dark patterns in the electric field profiles. The dependency of radiation pressure on the dielectric permittivity and supplied input frequency has been investigated. Further, we assessed the capabilities of neural networks to predict the radiation pressure for a given system. The proposed deep neural network model is aimed at developing accurate and efficient data-driven plasma surface wave devices.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2023

Effect of the filler morphology on the crystallization behavior and dielectric properties of the polyvinylidene fluoride‐based composite

Abstract Ceramic/polymer composites can be chemically stable, mechanically strong, and flexible, which make them candidates for electric devices, such as pressure or temperature sensors, energy storage or harvesting devices, actuators, and so forth. Depending on the application, various electrical properties are of importance. Polymers usually have low dielectric permittivity, but increased dielectric permittivity can be achieved by the addition of the ceramic fillers with high dielectric constant. With the aim to enhance dielectric properties of the composite without loss of flexibility, 5 wt% of BaTiO 3 ‐Fe 2 O 3 powder was added into a polyvinylidene fluoride matrix. The powder was prepared by different synthesis conditions to produce core/shell structures. The effect of the phase composition and morphology of the BaTiO 3 ‐Fe 2 O 3 core/shell filler on the structure and lattice dynamics of the polymer composites was investigated. Based on the results of the thermal analysis, various parameters of ceramic/polymer composites were determined. Differences in the phase composition and morphology of the filler have an influence on the formation of various polyvinylidene fluoride allomorphs and the degree of crystallinity. Furthermore, the dielectric performances of pure polyvinylidene fluoride and the polymer/ceramic composites were measured.

Polymer Science↗

NASA NTRS2009

The Thermal Electrical Conductivity Probe (TECP) for Phoenix

The Thermal and Electrical Conductivity Probe (TECP) is a component of the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) payload on the Phoenix Lander. TECP will measure the temperature, thermal conductivity and volumetric heat capacity of the regolith. It will also detect and quantify the population of mobile H2O molecules in the regolith, if any, throughout the polar summer, by measuring the electrical conductivity of the regolith, as well as the dielectric permittivity. In the vapor phase, TECP is capable of measuring the atmospheric H2O vapor abundance, as well as augment the wind velocity measurements from the meteorology instrumentation. TECP is mounted near the end of the 2.3 m Robotic Arm, and can be placed either in the regolith material or held aloft in the atmosphere. This paper describes the development and calibration of the TECP. In addition, substantial characterization of the instrument has been conducted to identify behavioral characteristics that might affect landed surface operations. The greatest potential issue identified in characterization tests is the extraordinary sensitivity of the TECP to placement. Small gaps alter the contact between the TECP and regolith, complicating data interpretation. Testing with the Phoenix Robotic Arm identified mitigation techniques that will be implemented during flight. A flight model of the instrument was also field tested in the Antarctic Dry Valleys during the 2007-2008 International Polar year. 2

Zent, Aaron P.↗

NASA NTRS2013

Damage Detection Response Characteristics of Open Circuit Resonant (SansEC) Sensors

The capability to assess the current or future state of the health of an aircraft to improve safety, availability, and reliability while reducing maintenance costs has been a continuous goal for decades. Many companies, commercial entities, and academic institutions have become interested in Integrated Vehicle Health Management (IVHM) and a growing effort of research into "smart" vehicle sensing systems has emerged. Methods to detect damage to aircraft materials and structures have historically relied on visual inspection during pre-flight or post-flight operations by flight and ground crews. More quantitative non-destructive investigations with various instruments and sensors have traditionally been performed when the aircraft is out of operational service during major scheduled maintenance. Through the use of reliable sensors coupled with data monitoring, data mining, and data analysis techniques, the health state of a vehicle can be detected in-situ. NASA Langley Research Center (LaRC) is developing a composite aircraft skin damage detection method and system based on open circuit SansEC (Sans Electric Connection) sensor technology. Composite materials are increasingly used in modern aircraft for reducing weight, improving fuel efficiency, and enhancing the overall design, performance, and manufacturability of airborne vehicles. Materials such as fiberglass reinforced composites (FRC) and carbon-fiber-reinforced polymers (CFRP) are being used to great advantage in airframes, wings, engine nacelles, turbine blades, fairings, fuselage structures, empennage structures, control surfaces and aircraft skins. SansEC sensor technology is a new technical framework for designing, powering, and interrogating sensors to detect various types of damage in composite materials. The source cause of the in-service damage (lightning strike, impact damage, material fatigue, etc.) to the aircraft composite is not relevant. The sensor will detect damage independent of the cause. Damage in composite material is generally associated with a localized change in material permittivity and/or conductivity. These changes are sensed using SansEC. The unique electrical signatures (amplitude, frequency, bandwidth, and phase) are used for damage detection and diagnosis. An operational system and method would incorporate a SansEC sensor array on select areas of the aircraft exterior surfaces to form a "Smart skin" sensing surface. In this paper a new method and system for aircraft in-situ damage detection and diagnosis is presented. Experimental test results on seeded fault damage coupons and computational modeling simulation results are presented. NASA LaRC has demonstrated with individual sensors that SansEC sensors can be effectively used for in-situ composite damage detection of delamination, voids, fractures, and rips. Keywords: Damage Detection, Composites, Integrated Vehicle Health Monitoring (IVHM), Aviation Safety, SansEC Sensors

Dudley, Kenneth L.↗