Temperature dependence of electrical conductivity and dielectric properties in Li–Mn ferrite

2014 ◽  
Vol 92 (6) ◽  
pp. 522-528 ◽  
Author(s):  
S.A. Mazen ◽  
N.I. Abu-Elsaad
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Properties ◽  
Room Temperature ◽  
Conduction Mechanism ◽  
Dielectric Behavior ◽  
Lithium Ferrite ◽  
Ac Conductivities ◽  
Polarization Process ◽  
Wide Range ◽  
Mn Content

Manganese substituted lithium–ferrite with the general formula Li0.5–0.5xMnxFe2.5–0.5xO4 (where x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0) were synthesized by the standard ceramic technique. The variation of DC and AC conductivities has been reported as a function of temperature from room temperature (293 K) up to 970 K in static air. AC measurements were carried out over a wide range of frequencies from 100 Hz up to 1 MHz. The variation ln σ at room temperature with composition indicates that the conductivity initially increases up to 0.5 and then decreases with further addition in Mn content. The activation energy of the conduction mechanism decreases from 0.68 to 0.34 eV. The electrical conductivity in the present ferrite is explained on the basis of the hopping mechanism. Dielectric properties, such as dielectric loss tangent, tanδ, and dielectric constant, ε′, have been measured. The dielectric behavior is explained by using the mechanism of the polarization process.

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.

AC CONDUCTIVITY AND DIELECTRIC PROPERTIES OF PMMA/FULLERENE COMPOSITES

2010 ◽  
Vol 24 (09) ◽  
pp. 911-919 ◽  
Author(s):  
G. M. NASR ◽  
R. M. AHMED
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Properties ◽  
Frequency Dependence ◽  
Room Temperature ◽  
Volume Fraction ◽  
Polymeric Composite ◽  
Dielectric Behavior ◽  
Fullerene C60 ◽  
Electrical Modulus ◽  
Frequency Range

Dielectric properties and electrical conductivity of different concentrations of Poly methylmethacrylate (PMMA)/fullerene C60 composites have been reported at room temperature in the frequency range from 1 kHz to 5 MHz. The frequency dependence of complex permittivity, ε*, and complex electrical modulus, M*, have been measured. Frequency dependence of dielectric constant, follows Cole–Cole dielectric relaxation equations, was investigated diagrammatically. Moreover, equations of Tsangaris et al. have been tested for our case to describe the dielectric behavior of particulate polymeric composite containing fillers which give a satisfactory agreement taking into account the variation of the aspect ratio with the volume fraction of fullerene C60 doped in the PMMA matrix.

scholarly journals Prediction Model of Asphalt Content of Asphalt Mixture Based on Dielectric Properties

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Yanhui Zhong ◽  
Yilong Wang ◽  
Bei Zhang ◽  
Xiaolong Li ◽  
Songtao Li ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Prediction Model ◽  
Room Temperature ◽  
Asphalt Mixture ◽  
Aggregate Size ◽  
Asphalt Pavements ◽  
Test Results ◽  
Wide Range ◽  
Asphalt Content ◽  
Ground Penetrating

The rapid detection of asphalt content in asphalt mixture is of great significance to the quality evaluation of asphalt pavement. Based on the dielectric properties of an asphalt mixture, the prediction model of asphalt content is deduced theoretically using three types of dielectric models: Lichtenecker-Rother (L-R) model, Rayleigh model, and Bottcher equation. Under the condition of laboratory mixing at room temperature (about 20–25°C), a dielectric test of asphalt mixture is conducted to verify the applicability of the model. The test results indicate that the dielectric constant of the asphalt mixture is inversely proportional to the asphalt content and directly proportional to the aggregate size of the mixture. Among the models, the Rayleigh model has a wide range of applications and exhibits a high accuracy, with an average relative error of only 1.86%. The results provide a theoretical basis for the nondestructive testing of asphalt pavements using ground-penetrating radar.

Electron transport and conduction band structure of GaSb

1981 ◽  
Vol 59 (12) ◽  
pp. 1844-1850 ◽  
Author(s):  
Hyung Jae Lee ◽  
John C. Woolley
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Electrical Conductivity ◽  
Conduction Band ◽  
Room Temperature ◽  
Energy Gap ◽  
Band Model ◽  
Scattering Coefficients ◽  
Wide Range ◽  
Different Temperatures

Calculations have been made using the Fletcher and Butcher method in a three conduction band model to fit a wide range of experimental transport data for n-type samples of GaSb: viz. Hall coefficient and electrical conductivity as a function of temperature and as a function of pressure at room temperature, magnetoresistance as a function of magnetic field at different temperatures, and Nernst–Ettingshausen coefficients as a function of magnetic field. Various energy gap parameters and scattering coefficients have been taken as adjustable and values determined for these which give good fits to all of the experimental data. Values of mobility for each of the Γ, L, and X bands have then been calculated as a function of temperature.

scholarly journals Porous and Nonporous Film-Shaped Magnetorheological Nanocomposites: Dielectric and Electrical Properties

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Aref Naimzad ◽  
Yousef Hojjat ◽  
Mojtaba Ghodsi
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Room Temperature ◽  
Volume Resistivity ◽  
Comparative Investigation ◽  
Dielectric Constants ◽  
Dielectric Losses ◽  
Iron Particles ◽  
Electrical And Dielectric Properties

This paper presents a brief experimental comparative study on electrical and dielectric properties of two sets of porous and nonporous MRNCs, each including five samples of film-shaped magnetorheological nanocomposites (MRNCs) based on room temperature vulcanized (RTV) silicone rubber and nanosized carbonyl iron particles (CIPs). The electrical and dielectric properties of porous and nonporous MRNCs were measured at five different filler concentrations. Several experiments were performed to measure the volume resistivity, dielectric constant, and dielectric loss. The MRNCs dielectric properties were analysed with respect to the parameters like frequency and CIPs loadings. The electrical conductivity was studied in terms of volume resistivity. The comparative investigation suggests the porous MRNCs for smart and light-weighted structures those benefits from a lower electrical property, dielectric losses, and dielectric constants.

scholarly journals Conductivity and Dielectric Behaviour Studies of LiCF3SO3 Dissociation in L-Chitosan/PMMA-Based Polymer Electrolytes

2013 ◽  
Vol 9 (1) ◽  
Author(s):  
A.S.A Khiar ◽  
S. Mat Radzi ◽  
N. Abd Razak
Keyword(s):  
Relaxation Time ◽  
Dielectric Properties ◽  
Ionic Conductivity ◽  
Polymer Electrolytes ◽  
Room Temperature ◽  
Electrical Modulus ◽  
Solution Casting ◽  
Casting Method ◽  
Wide Range ◽  
Solution Casting Method

Lauroyl-chitosan/poly(methylmethacrylate)-lithium trifluorosulfonate (LiCF3SO3) polymer electrolytes has been prepared by the solution casting method. Ionic conductivity analysis was conducted over a wide range of frequency between 50 Hz-1 MHz using impedance spectroscopy to evaluate the dielectric properties and conductivity of the sample. Sample with 30 wt% of LiCF3SO3 showed the highest conductivity of 7.59 ± 3.64 x 10-4 Scm-1 at room temperature. Complex permittivity for real (εr), imaginary (εi) and electrical modulus for real (Mr) and imaginary (Mi) part was determined and plotted. The relaxation time, τ for these samples was determined and the plot shows that τ decreases with conductivity of the complexes.

scholarly journals N-Type Thermoelectric Textile Fabrics Based on Vapor Grown Carbon Nanofibers

2020 ◽  
Vol 2 (1) ◽  
pp. 10
Author(s):  
S. Machado ◽  
E. M. F. Vieira ◽  
A. M. Rocha ◽  
A. J. Paleo
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Carbon Nanofibers ◽  
Room Temperature ◽  
Thermoelectric Module ◽  
Multiwall Carbon Nanotubes ◽  
Chemical Vapor ◽  
Textile Fabrics ◽  
Wide Range ◽  
P Type

Thermoelectric (TE) devices that convert a heat gradient directly into electricity are considered as a clean technology for energy harvesting. Both hole-transporting (p-type) and electron-transporting (n-type) materials are required in order to fabricate a thermoelectric module. Carbon nanotube (CNT)-based textile fabrics are relevant in this context for the production of wearable TE modules due to the combination of the high electrical conductivity and thermopower (Seebeck coefficient) from the CNT and the low thermal conductivity and flexibility provided by the textile fabric [1]. Nevertheless, most as-produced CNTs are p-type materials due to their inherent oxygen doping, and therefore the production of air- and thermally stable n-type CNT-based textile fabrics remains a challenge nowadays [2]. On the other hand, vapor-grown carbon nanofibers (VGCNF), produced by chemical vapor deposition (CVD), have similar structures to multiwall carbon nanotubes (MWCNT), which make them valuable for electronic applications. For instance, by adjusting process variables during their CVD and post-growth heat treatment, VGCNF can be tailored to have a wide range of thermal conductivity and electrical conductivity at room temperature. In particular, the unexpected n-type character at room temperature that they supply to dip-coated cotton fabrics will be the issue of this presentation [3].

AC Conductivity and Dielectric Properties of BiScO3–PbTiO3 Piezoelectric Ceramics

2021 ◽  
Vol 13 (9) ◽  
pp. 1807-1811
Author(s):  
Jae-Hoon Ji ◽  
Yoo-Young Oh ◽  
Bo Su Kim ◽  
Wook-Hee Han ◽  
Jung-Hyuk Koh
Keyword(s):  
Dielectric Properties ◽  
Electrical Properties ◽  
Ac Conductivity ◽  
Piezoelectric Properties ◽  
Piezoelectric Materials ◽  
Ferroelectric Properties ◽  
Temperature Stability ◽  
Piezoelectric Ceramics ◽  
Dielectric Behavior ◽  
Wide Range

Bi-based BiMeO3 (where Me is a transition metal) has been extensively studied owing to its outstanding ferroelectric properties. The dielectric and electrical properties of piezoelectric ceramics can be enhanced by the addition of Bi-based materials such as BiAlO3, BiScO3 , and Bi(Mg, Ti)O3. Among them, BiScO3–PbTiO3 ceramics have shown excellent piezoelectric properties and temperature stability near the morphotropic phase boundary (MPB) region. Meanwhile, it is important to study the electrical properties of piezoelectric materials such as dielectric permittivity, conductivity of ferroelectric compounds, since dielectric and conductivities are related to pyroelectricity and piezoelectricity. In this study, the AC conductivity and dielectric properties of BiScO3–PbTiO3 ceramics were investigated with a wide range of frequencies and temperatures. Especially,the effect of PbTiO3 content on dielectric behavior of the BiScO3–PbTiO3 system was intensively studied by impedance spectroscopy.

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