High-voltage bridge for measuring spontaneous polarization, dielectric constants, and conductivity of ferroelectric crystals

1989 ◽  
Vol 32 (9) ◽  
pp. 888-890
Author(s):  
I. N. Polandov ◽  
V. K. Novik ◽  
O. K. Gulish ◽  
B. P. Bogomolov ◽  
V. B. Morozov
Keyword(s):  
High Voltage ◽  
Spontaneous Polarization ◽  
Dielectric Constants ◽  
Ferroelectric Crystals

scholarly journals The Effects of Aluminum-Nitride Nano-Fillers on the Mechanical, Electrical, and Thermal Properties of High Temperature Vulcanized Silicon Rubber for High-Voltage Outdoor Insulator Applications

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3562 ◽  
Author(s):  
Chang Liu ◽  
Yiwen Xu ◽  
Daoguang Bi ◽  
Bing Luo ◽  
Fuzeng Zhang ◽  
...  
Keyword(s):  
Contact Angle ◽  
Thermal Properties ◽  
High Temperature ◽  
High Voltage ◽  
Breakdown Strength ◽  
Electrical Breakdown ◽  
Theoretical Models ◽  
Dielectric Constants ◽  
Silicon Rubber ◽  
Electrical Breakdown Strength

AlN nanoparticles were added into commercial high-temperature-vulcanized silicon rubber composites, which were designed for high-voltage outdoor insulator applications. The composites were systematically studied with respect to their mechanical, electrical, and thermal properties. The thermal conductivity was found to increase greatly (>100%) even at low fractions of the AlN fillers. The electrical breakdown strength of the composites was not considerably affected by the AlN filler, while the dielectric constants and dielectric loss were found to be increased with AlN filler ratios. At higher doping levels above 5 wt% (~2.5 vol%), electrical tracking performance was improved. The AlN filler increased the tensile strength as well as the hardness of the composites, and decreased their flexibility. The hydrophobic properties of the composites were also studied through the measurements of temperature-dependent contact angle. It was shown that at a doping level of 1 wt%, a maximum contact angle was observed around 108°. Theoretical models were used to explain and understand the measurement results. Our results show that the AlN nanofillers are helpful in improving the overall performances of silicon rubber composite insulators.

Calculations of the Spontaneous Polarizations and Dielectric Constants for AlN, GaN, InN, and SiC

2010 ◽  
Vol 645-648 ◽  
pp. 1203-1206
Author(s):  
Sergey Y. Davydov ◽  
Alexander A. Lebedev
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Spontaneous Polarization ◽  
Reasonable Agreement ◽  
Low Frequency ◽  
Analytical Form ◽  
Dielectric Constants ◽  
Numerical Calculations ◽  
Ab Initio Methods ◽  
Theoretical Results

Within the scope of the Harrison’s bond orbital model the spontaneous polarization, high- and low frequency dielectric constants are obtained in an analytical form. Theoretical results are in a reasonable agreement with the experimental data available and the numerical calculations based on the ab initio methods.

A self-consistent polycrystal model for the spontaneous polarization of ferroelectric ceramics

2006 ◽  
Vol 462 (2070) ◽  
pp. 1763-1789 ◽  
Author(s):  
Y Su ◽  
G.J Weng
Keyword(s):  
Curie Temperature ◽  
Electric Field ◽  
Spontaneous Polarization ◽  
Mixture Theory ◽  
Temperature Shift ◽  
Dielectric Constants ◽  
Ferroelectric Ceramics ◽  
Consistent Model ◽  
Self Consistent ◽  
Polycrystalline Ceramic

Motivated by the observation that the spontaneous polarization process of a ferroelectric polycrystal under the influence of a superimposed stress and/or electric field involves heterogeneous evolution of the ferroelectric phase among its constituent grains, a self-consistent electromechanical model is developed to determine the effective behaviour of the polycrystalline ceramic from such a heterogeneous electromechanical state. We start out from consideration of a micromechanics-based thermodynamic process to establish the kinetic equation of the crystallite and use it to evaluate the evolution of its ferroelectric domain. Then together with the Curie–Weiss law for the dielectric constants of the tetragonal phase, a dual-phase mixture theory is adopted to determine the change of its electromechanical moduli as temperature cools down below its Curie point. The overall property of the polycrystal is subsequently calculated by the self-consistent model through orientational average over its constituent grains. This two-level micromechanics model is applied to examine the shift of Curie temperature and evolution of the effective electromechanical moduli of a BaTiO 3 ceramic under cooling. The calculated results show that its Curie temperature decreases with increasing hydrostatic pressure, but increases with a superimposed axial compression or a biased electric field. The predicted temperature shift and change of the dielectric constants are found to be consistent with experimental observations.

Thin-film High Voltage Capacitors for Hybrid Electric Vehicle Inverter Applications

2012 ◽  
Vol 2012 (1) ◽  
pp. 001116-001123
Author(s):  
M. Ray Fairchild ◽  
Carl W. Berlin ◽  
D.H.R. Sarma ◽  
Ralph S. Taylor ◽  
Han S. Lee ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Failure Mode ◽  
High Voltage ◽  
Hybrid Electric Vehicle ◽  
Argonne National Laboratory ◽  
Dielectric Constants ◽  
Metal Foil ◽  
Equivalent Series Resistance ◽  
Source Power ◽  
Hybrid Electric

The propulsion system in hybrid electric vehicles (HEVs) requires an alternating current (AC) electric motor in combination with an internal combustion engine. When the HEV is being propelled by the AC motor, the power for the motor is provided by batteries whose direct current (DC) voltage is chopped into an AC waveform via an electronic device called a power inverter. Capacitors known as DC bulk capacitors are placed between the battery and the inverter to “decouple” the AC switching inverter from the power source. Power electronics inverters use several large high voltage discrete DC bulk capacitors, which negatively influence the inverter's size, weight and are a high cost item in the assembly. The use of a high dielectric constant (Dk) ferroelectric material enables smaller, higher temperature capable, lower-cost power capacitors. Ceramic ferroelectrics, such as (Pb,La)(Zr,Ti)O3 [PLZT], offer the highest dielectric constants. Argonne National Laboratory is developing a novel film-on-foil technology for high-power capacitors utilizing PLZT. These capacitors, with an increasing dielectric constant with temperature, low equivalent series resistance and a benign failure mode, are well suited for power applications. The PLZT is deposited onto a metal foil via a chemical deposition process and the top electrode metal (Pt or Al) is then deposited by electron beam evaporation onto the top surface of the dielectric thus creating the capacitor. This project involved the fabrication and electrical evaluation of film-on-foil capacitors for HEV inverter applications. Capacitors utilizing both nickel and platinum-on-silicon as the base substrate, and PLZT as the dielectric material were fabricated. These capacitors were tested for dielectric integrity, capacitance, voltage breakdown, and benign failure mode. Results from these mechanical and electrical evaluation tests will be presented. Key processing challenges and implementation methods will also be described.

High Voltage Electron Microscopy of Ion-Milled Dental Enamel

1974 ◽  
Vol 32 ◽  
pp. 60-61
Author(s):  
L. D. Ackerman ◽  
S. H. Y. Wei
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Third Molar ◽  
Polarized Light ◽  
Dental Enamel ◽  
Longitudinal Section ◽  
Ion Milling ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
High Voltage Electron

Mature human dental enamel has presented investigators with several difficulties in ultramicrotomy of specimens for electron microscopy due to its high degree of mineralization. This study explores the possibility of combining ion-milling and high voltage electron microscopy as a means of circumventing the problems of ultramicrotomy.A longitudinal section of an extracted human third molar was ground to a thickness of about 30 um and polarized light micrographs were taken. The specimen was attached to a single hole grid and thinned by argon-ion bombardment at 15° incidence while rotating at 15 rpm. The beam current in each of two guns was 50 μA with an accelerating voltage of 4 kV. A 20 nm carbon coating was evaporated onto the specimen to prevent an electron charge from building up during electron microscopy.

Three-Dimensional Visualization of the T-System of Frog Muscle Using High Voltage Electron Microscopy and a Lanthanum Stain

1977 ◽  
Vol 35 ◽  
pp. 570-571 ◽  
Author(s):  
Lee D. Peachey ◽  
Clara Franzini-Armstrong
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Three Dimensional ◽  
Biological Tissues ◽  
High Voltage Electron Microscopy ◽  
Transverse Tubular System ◽  
Peroxidase Reaction ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
T System

The effective study of biological tissues in thick slices of embedded material by high voltage electron microscopy (HVEM) requires highly selective staining of those structures to be visualized so that they are not hidden or obscured by other structures in the image. A tilt pair of micrographs with subsequent stereoscopic viewing can be an important aid in three-dimensional visualization of these images, once an appropriate stain has been found. The peroxidase reaction has been used for this purpose in visualizing the T-system (transverse tubular system) of frog skeletal muscle by HVEM (1). We have found infiltration with lanthanum hydroxide to be particularly useful for three-dimensional visualization of certain aspects of the structure of the T- system in skeletal muscles of the frog. Specifically, lanthanum more completely fills the lumen of the tubules and is denser than the peroxidase reaction product.

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