Cu0.5K0.25Tl0.25Ba2Ca3Cu4O12-δ SUPERCONDUCTOR AND ITS DIELECTRIC PROPERTIES

2010 ◽  
Vol 24 (32) ◽  
pp. 3097-3107
Author(s):  
ADNAN YOUNIS ◽  
NAWAZISH ALI KHAN
Keyword(s):  
Dielectric Properties ◽  
Loss Factor ◽  
Dielectric Constants ◽  
Negative Capacitance ◽  
Test Frequency ◽  
Ceramic Superconductor ◽  
Thermal Agitation ◽  
Metal Electrodes ◽  
Low Frequencies ◽  
Tan Δ

Cu 0.5 K 0.25 Tl 0.25 Ba 2 Ca 3 Cu 4 O 12-δ superconductor samples were synthesized and their dielectric properties were measured between 80 K and 290 K by means of capacitance (C) and conductance (G) measurements with the test frequency (f) in the range of 10 KHz to 4 MHz. A negative capacitance (NC) occurrence was observed, which most likely arose from the superior Fermi level of ceramic superconductor samples than metal electrodes. Also the NC may be due to the space charge situated at the multiple insulator–superconductor interfaces (grain boundaries) in the materials. The negative dielectric constant (ε′) and loss factor ( tan δ) show strong dispersion at low frequencies. The lower thermal agitation at 80 K may boost the polarizability and hence the dielectric constants (ε′ and ε″).

scholarly journals Dielectric Properties of Wood-Polymer Composites: Effects of Frequency, Fiber Nature, Proportion, and Chemical Composition

2021 ◽  
Vol 5 (6) ◽  
pp. 141
Author(s):  
Imen Elloumi ◽  
Ahmed Koubaa ◽  
Wassim Kharrat ◽  
Chedly Bradai ◽  
Ahmed Elloumi
Keyword(s):  
Dielectric Properties ◽  
Polymer Composites ◽  
Wide Frequency Range ◽  
Dielectric Constants ◽  
Cellulose Content ◽  
Wood Fibers ◽  
Low Frequencies ◽  
Wood Polymer ◽  
Wood Polymer Composites ◽  
New Applications

The characterization of the dielectric properties of wood–polymer composites (WPCs) is essential to understand their interaction with electromagnetic fields and evaluate their potential use for new applications. Thus, dielectric spectroscopy monitored the evolution of the dielectric properties of WPCs over a wide frequency range of 1 MHz to 1 GHz. WPCs were prepared using mixtures of different proportions (40%, 50%, and 60%) of wood and bark fibers from various species, high-density polyethylene, and maleated polyethylene (3%) by a two-step process, extrusion and compression molding. Results indicated that wood fibers modify the resistivity of polyethylene at low frequencies but have no effect at microwave frequencies. Increasing the fiber content increases the composites’ dielectric properties. The fibers’ cellulose content explains the variation in the dielectric properties of composites reinforced with fibers from different wood species. Indeed, composites with high cellulose content show higher dielectric constants.

Dielectric analysis of polypropylene (PP) and polylactic acid (PLA) blends reinforced with halloysite nanotubes

2017 ◽  
Vol 31 (8) ◽  
pp. 1042-1053 ◽  
Author(s):  
Krishna Prasad Rajan ◽  
Ahmed Al-Ghamdi ◽  
Selvin P Thomas ◽  
Aravinthan Gopanna ◽  
Murthy Chavali
Keyword(s):  
Dielectric Properties ◽  
Polylactic Acid ◽  
Loss Factor ◽  
Halloysite Nanotubes ◽  
Dynamic Mechanical Properties ◽  
Dielectric Analysis ◽  
Melt Mixing ◽  
Microelectronic Devices ◽  
Base Matrix ◽  
Tan Δ

Polypropylene (PP) and polylactic acid were blended in the ratio 80:20 by weight and compatibilized with 3 wt% of maleic anhydride-grafted-PP. The compatibilized blend was chosen as the base matrix for reinforcement with halloysite nanotubes (HNTs). The nanotube content varied from 0 to 10 wt%. Blend and the nanocomposites were prepared by melt mixing technique. Dielectric analysis of the base matrix and the nanocomposites was carried out using interdigitated electrode sensor in a DEA 288 Epsilon-dielectric analyser. The dielectric properties of the composites were measured at temperatures from 30 to 120°C at various frequencies ranging from 1 Hz to 1 kHz. Permittivity values slightly decreased as the HNT content increased from 0 to 2 wt%. It increased at 4 wt% of HNT and again slightly decreased at 6 wt% of HNT, and with further increase in HNT (HNT 8 and HNT 10) led to increase in permittivity values. Loss factor values decreased slightly as the HNT content in the composites increased from 0 to 4 wt%; but with further increase in HNT, the loss factor showed a sharp increase. Loss tangent (tan δ) values decreased up to 4 wt% of HNT (HNT 4) and then increased up to 8 wt% (HNT 8) of HNT and then decreased slightly (for HNT 10). Analysing the different dielectric properties, consistent properties were shown by 6 wt% of HNT similar to static and dynamic mechanical properties. The analysis showed that the composites can be utilized in microelectronic devices or in microelectronic packaging applications.

Multi-Component Mixture Modeling for the Dielectric Properties of Rubber Wood at Microwave Frequencies

Holzforschung ◽  
1999 ◽  
Vol 53 (6) ◽  
pp. 662-668 ◽  
Author(s):  
K.B. Khalid ◽  
M.F. Kabir ◽  
W. M. Daud ◽  
H.A.A. Sidek
Keyword(s):  
Experimental Data ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Loss Factor ◽  
Dielectric Constants ◽  
Dielectric Loss Factor ◽  
Component Mixture ◽  
Microwave Frequencies ◽  
Conductive Loss ◽  
Rubber Wood

Summary Dielectric properties from 1 to 18 GHz of rubber wood are modeled using generalized mixture equations and also with equations proposed by Weiner, Kraszewski, Looyenga and Landou, Lichtenecker. Dielectric properties were measured with an open-ended coaxial line-sensor in three structural directions longitudinal, radial and tangential and at different moisture contents. The dielectric constants were predicted well by the Weiner model for all structural grain directions and it was found that the degree of binding decreases with increasing frequency. However, the Weiner model cannot be used for predicting the dielectric loss factor at frequencies below 3 GHz. This may be due to the high conductive loss in this frequency region. The lower value of the exponents in generalized mixture equation was found suitable for fitting the experimental data as well as the Kraszewski equation. Values predicted by Lichtenecker equations are in well agreement with the experimental data at higher microwave frequencies. The prediction of dielectric loss factor using Kraszewski, Looyenga equations were not possible at frequencies below 3 GHz since it is dominated by conductive loss. Above 3 GHz, it was well predicted by Kraszewski and Looyenga equations.

Effect of thermal plasma heating on the dielectric properties of Al-Zr composites

2002 ◽  
Vol 216 (2) ◽  
pp. 127-132
Author(s):  
D R Sahu ◽  
B K Roul ◽  
S K Singh ◽  
R N P Chaudhury
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Thermal Plasma ◽  
Loss Factor ◽  
Gas Flow ◽  
Plasma Heating ◽  
Sintered Sample ◽  
Dielectric Measurement ◽  
Sintering Time ◽  
Tan Δ

A low-cost extended arc thermal plasma heating (EATPH) source has been used for the sintering of Al-Zr high-temperature ceramic oxides, and their dielectric properties have been studied. Pellets of Al-Zr composites were sintered using optimum sintering parameters such as sintering time, plasma power and plasmagen gas flow rate in an EATPH reactor. Samples of similar composites were also sintered using a conventional resistive heating furnace at 1500°C for 20 h, and their dielectric properties were studied and compared with the plasma sintered sample. Sintered pellets were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and dielectric measurement, carried out as a function of frequency and temperature. Highly dense sintered products were obtained by the plasma heating route within a very short sintering time compared with the conventional sintering schedule. Dielectric measurements (both dielectric constant and loss factor) showed a significant reduction in the dielectric constant, K, at room temperature under different test frequencies and also as a function of temperature. However, the change in dielectric loss factor, tan Δ, was not as pronounced as the change in K. The behaviour of the K and tan Δ curves changes drastically compared with the conventional sintered material. The reduction in K and the crossover behaviour of tan Δ in the plasma sintered specimen may be due to the action of non-reactive Ar plasmagen gas during plasma sintering, which favours mobile oxygen for the polarization network under the influence of frequency and temperature.

Dielectric Properties of Blackberries as Related to Microwave Drying Control

2017 ◽  
Vol 13 (12) ◽  
Author(s):  
Chunfang Song ◽  
Tian Sang ◽  
Haiying Chen ◽  
Li Zhenfeng ◽  
Li Jing
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Moisture Content ◽  
Penetration Depth ◽  
Loss Factor ◽  
Large Scale ◽  
Coaxial Line ◽  
Dielectric Constants ◽  
Microwave Drying ◽  
Increasing Temperature

AbstractThe dielectric properties of blackberry samples with a 20.0–80.0 % w.b (web basis) moisture content were determined with a network analyzer and an open-ended coaxial-line probe over a frequency range from 5 to 3000 MHz and a temperature range from 20 to 100 °C. The results showed that the dielectric constant decreased with increasing temperature but increased with increasing moisture content; however, the loss factor increased with increasing temperature and moisture content. The dielectric constant and the loss factor decreased with increasing frequency. The penetration depth decreased with increasing temperature, frequency and moisture content. A large penetration depth at 915 MHz may provide practical large-scale dielectric drying for blackberries. The dielectric constants and loss factors for blackberry by combining the above mathematical model and temperature and moisture of the sample in the microwave drying process were used to analyze and control blackberry drying technology.

scholarly journals Molecular Weight Enables Fine-Tuning the Thermal and Dielectric Properties of Polymethacrylates Bearing Sulfonyl and Nitrile Groups as Dipolar Entities

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 317
Author(s):  
Sebastian Bonardd ◽  
Cesar Saldías ◽  
Ángel Leiva ◽  
David Díaz Díaz ◽  
Galder Kortaberria
Keyword(s):  
Molecular Weight ◽  
Dielectric Properties ◽  
Dielectric Constants ◽  
Polymer Materials ◽  
Fine Tuning ◽  
Molecular Weights ◽  
Dielectric Performance ◽  
Tan Δ ◽  
High Dielectric ◽  
Loss Factors

In this work, polymethacrylates containing sulfonyl and nitrile functional groups were successfully prepared by conventional radical polymerization and reversible addition-fragmentation chain-transfer polymerization (RAFT). The thermal and dielectric properties were evaluated, for the first time, considering differences in their molecular weights and dispersity values. Variations of the aforementioned properties do not seem to substantially affect the polarized state of these materials, defined in terms of the parameters ε’r, ε”r and tan (δ). However, the earlier appearance of dissipative phenomena on the temperature scale for materials with lower molecular weights or broader molecular weight distributions, narrows the range of working temperatures in which they exhibit high dielectric constants along with low loss factors. Notwithstanding the above, as all polymers showed, at room temperature, ε’r values above 9 and loss factors below 0.02, presenting higher dielectric performance when compared to conventional polymer materials, they could be considered as good candidates for energy storage applications.

Microstructure and Dielectric Properties of BaFe12O19 Hexaferrite Nanoparticles: Effect of Cobalt Addition and Calcination Temperature

2020 ◽  
Vol 13 (3) ◽  
pp. 211-219
Keyword(s):  
Dielectric Properties ◽  
Barium Hexaferrite ◽  
Hexagonal Structure ◽  
Dielectric Constants ◽  
Precipitation Method ◽  
Calcination Temperatures ◽  
Transmission Electron ◽  
Tan Δ ◽  
Co Addition ◽  
Co Precipitation

Abstract: M-type Barium Hexaferrite (BaFe12O19) is a promising compound for technological applications because of its high permeability, high saturation magnetization and excellent dielectric properties. In this study, the microstructure and dielectric properties of CoxBaFe12O19Hexaferrite were investigated. The co-precipitation method was employed to prepare CoxBaFe12O19 nanoparticles, with x = 0, 0.04, 0.06 and 0.1 wt. %, at two different calcination temperatures (900oC and 950oC). The microstructure of the samples was examined through X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The hexagonal structure of the prepared samples was confirmed from XRD results. TEM images reveal the formation of agglomerated nanoparticles with different size distribution. The dielectric properties of the samples were studied through HIOKI 3532-50 LCR-Hi TESTER as a function of frequency (100 kHz–3MHz) and temperature (25 °C–500°C). The effects of Co addition, frequency and temperature on the dielectric constants (ɛʹ and ɛʹʹ), loss tangent (tan δ) and ac conductivity (σac) have been explained on the basis of hopping of electrons between Fe2+ and Fe3+ ions. Keywords: BaFe12O19 Hexaferrite, Co-precipitation method, XRD, Dielectric properties.

Dielectric Properties of W-Type BaCa2Fe16O27 Hexaferrite Prepared Using a Stearic Acid Gel Route

2013 ◽  
Vol 665 ◽  
pp. 210-213 ◽  
Author(s):  
Chetna C. Chauhan ◽  
Rajshree B. Jotania
Keyword(s):  
Dielectric Properties ◽  
Dielectric Loss ◽  
Stearic Acid ◽  
Room Temperature ◽  
Conduction Mechanism ◽  
Dielectric Behavior ◽  
Dielectric Constants ◽  
Tan Δ ◽  
Acid Gel ◽  
Hopping Model

W-type hexagonal ferrite with composition BaCa2Fe16O27 was prepared using a stearic acid gel method. The precipitate of barium calcium hexaferrite was calcinated at 650°C, 750°C, 850°C and 950°C in a furnace for 4 hours and then slowly cooled to room temperature. The dielectric constants (real Є and imaginary Є), conductivity (σ) and dielectric loss (tan δ) have been measured at room temperature as a function of frequency (102-106 Hz). The dielectric behavior of prepared hexaferrite samples can be explained by the mechanism of polarization and the electrical conduction mechanism is explained by using the electronic hopping model of Heike Johnson.

scholarly journals Using a Dielectric Capacitance Cell to Determine the Dielectric Properties of Pure Sand Artificially Contaminated with Pb, Cd, Fe, and Zn

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Mohammed Dahim ◽  
Musab Abuaddous ◽  
Rabah Ismail ◽  
Hashem Al-Mattarneh ◽  
Aiman Jaradat
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Loss Factor ◽  
Simple Calculation ◽  
Dielectric Constants ◽  
Pollution Level ◽  
Dielectric Capacitance ◽  
Capacitance Cell

This paper presents a new method of dielectric capacitance cell as a proposed device for measuring the impedance of pure sand artificially contaminated with four heavy metals. Dielectric constant and loss factor of clean and contaminated sand at various levels were calculated from the measured sand impedances. The advantages and benefits of using the proposed dielectric capacitance cell were its low cost, simple calculation, calibration procedures, portable and lightweight, and easy to modify the electrodes to suit testing in the field. Pure sand was saturated with water artificially polluted in the lab with Pb, Cd, Fe, and Zn at heavy metal contents 0, 7.5, 15, 22.5, and 30 mg/kg of sand. The dielectric properties of polluted sand were evaluated at a frequency range from 100 kHz to 1000 kHz. The polluted sand exhibit different dielectric constants and loss factors from the unpolluted sand. The results also indicate that the dielectric constant decreases with increasing pollution level for all heavy metals. This may attribute to the polarization mechanism change with existing heavy metal. The loss factor of sand increases with the increasing pollution level. This may be explained by the increase of ionic conductivity of pore water with heavy metal in the sand. Sand polluted with heavy metal with higher resistivity and density possess a higher dielectric constant and lower loss factor than other polluted metals. Evaluation of the dielectric characteristics of polluted sand could have the potential to monitor heavy metal pollution. Even with promising results obtained with the proposed dielectric device, it is necessary to explore several other factors affecting the measurements such as sand water content, soil texture, and type of soil. Also, testing polluted soil near industrial pollution is needed.

scholarly journals Dielectric Properties of Switchgrass and Corn Stover in the Radio Frequency Range

2021 ◽  
Vol 64 (1) ◽  
pp. 243-252
Author(s):  
Augusto M. Souza ◽  
Stuart J. Birrell ◽  
Brian L. Steward
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Moisture Content ◽  
Radio Frequency ◽  
Corn Stover ◽  
Loss Factor ◽  
Prediction Models ◽  
Dielectric Constants ◽  
Frequency Range ◽  
Loss Factors

HighlightsDielectric permittivities of switchgrass and corn stover in the radio frequency range were calculated.Prediction models achieved R2 > 0.9, except for the switchgrass loss factor for the material in motion.The loss factors were different when static and in motion, but the dielectric constants were similar.Abstract. The dielectric properties of biological materials are relevant when developing moisture content sensors. However, little is known about the permittivities of switchgrass and corn stover in a wider frequency range. The goal of this research was to determine their dielectric constants and loss factors at different moisture contents across a frequency range of 5 Hz to 13 MHz and with the material static and in motion inside a sample container. The permittivity of these materials was calculated by measuring their admittance in a test fixture using an impedance analyzer at three different moisture levels (9.0% to 30.5%). Overall, the materials’ dielectric properties increased with moisture but decreased with frequency. Prediction models were developed using the data in a frequency range of 10 kHz to 5 MHz. Model coefficients of determination were higher than 0.90 in general, except for the model measuring the loss factor of switchgrass in motion. Additionally, the dielectric constant was not different with the materials static or in motion, but the loss factor values were distinct. This work can be used for the development of electrical moisture content sensors for switchgrass and corn stover. Keywords: Corn stover, Dielectric constant, Loss factor, Moisture content, Permittivity, Switchgrass.

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