Frequency Dependent Dielectric Permittivity Studies in Emeraldine Base and Weakly Doped Polyaniline and its Deriviatives

1999 ◽  
Vol 598 ◽  
Author(s):  
Nicholas J. Pintoa ◽  
Ghanshyam P. Sinha ◽  
Fouad M. Aliev
Keyword(s):  
Dielectric Permittivity ◽  
Dielectric Relaxation ◽  
Doping Level ◽  
Relaxation Times ◽  
Relaxation Mechanism ◽  
Emeraldine Base ◽  
Three Samples ◽  
Multiple Paths ◽  
Doped Polyaniline ◽  
Subsequent Diffusion

ABSTRACTWe report on a study of the complex dielectric permittivity in polyaniline (PAN), poly-o-toluidine (POT) and poly-o-ethylaniline (OPEA) in the undoped and weakly doped state in the frequency range 1 mHz upto 1 MHz. The doping concentration defined as y=[C1-]/[N] was chosen so that 0 ≤ y ≤ 0.07. OPEA with y=0.50 was also investigated. The objective of this work was to investigate the contribution of the mobile charge defects (polarons and bipolarons) on the conductivity and dielectric relaxation at such low doping levels. The three samples were chosen so as to compare the effects of introducing larger interchain disorder while maintaining a similar conduction mechanism. In all samples studied we observe the presence of a dielectric relaxation mechanism and the relaxation times depend on the doping level and disorder. The presence of a larger number of polarons as the doping level is increased leads to multiple paths for the system to relax leading to progressively non Debye like relaxation process. The results are interpreted in terms of creation and annihilation of polarons and bipolarons and their subsequent diffusion.

Dielectric relaxation of acetyl- and benzoyl-acetones

1989 ◽  
Vol 67 (5) ◽  
pp. 804-808 ◽  
Author(s):  
R. K. Khanna ◽  
Abha Bhatnagar
Keyword(s):  
Dielectric Relaxation ◽  
Dipole Moments ◽  
Relaxation Times ◽  
Weight Fraction ◽  
Relaxation Mechanism ◽  
Relaxation Processes ◽  
Dielectric Absorption ◽  
Molar Polarization ◽  
Distribution Parameters ◽  
Few Data

Dielectric absorption measurements are reported at radio and microwave frequencies (at six different wavelengths) for acetylacetone and benzoylacetone solutions in benzene, in a temperature range 25–60 °C. Analysis of dielectric data in terms of Cole–Cole arc plots and multiple relaxation processes reveals that, at higher temperatures, overall molecular relaxation is the dominant relaxation mechanism in these β-diketones. The observed relaxation times, distribution parameters, and dipole moments are in reasonable agreement with the few data reported for some temperatures, in the literature. The activation energy parameters are also evaluated assuming dielectric relaxation to be a rate process. Molar polarization vs. weight fraction (concentration) plots show anomalous behaviour for acetylacetone. Keywords: dielectric properties, dielectric losses, relaxation times, dipole moment, dielectric absorption and dispersion, microwave measurements.

Dielectric relaxation studies. III. Allyl bromide and allyl ethers in liquid state

1981 ◽  
Vol 59 (11) ◽  
pp. 1690-1695
Author(s):  
M. Jeyaraj ◽  
J. Sobhanadri
Keyword(s):  
Dielectric Relaxation ◽  
Allyl Bromide ◽  
Relaxation Times ◽  
Activation Parameters ◽  
Relaxation Mechanism ◽  
Microwave Frequencies ◽  
Allyl Ethers ◽  
Dielectric Data ◽  
Permittivity Measurements ◽  
Allyl Compounds

Complex dielectric permittivity measurements are reported at radio and microwave frequencies for four allyl compounds in the temperature range 30–70 °C. The analysis of dielectric data in terms of Cole–Cole arc, multiple relaxation times, and Higasi's distribution function reveals that the overall molecular rotation is the dominant relaxation mechanism in these unsaturated compounds. The activation parameters are evaluated assuming dielectric relaxation to be a rate process.

Dielectric Relaxation of Long Molecules in Nematic Host Matrices

1982 ◽  
Vol 37 (3) ◽  
pp. 266-270
Author(s):  
Paul G. Gerber
Keyword(s):  
Dielectric Permittivity ◽  
Temperature Dependence ◽  
Dielectric Relaxation ◽  
Homologous Series ◽  
Relaxation Times ◽  
Guest Molecules ◽  
Structural Details ◽  
Host Matrices ◽  
Increasing Temperature

Abstract The relaxation times τ of the slowest processes in the parallel dielectric permittivity of various nematic guest-host systems have been measured as a function of temperature. A correlation between τ and its temperature dependence is found, indicating increasing temperature dependence for increasing τ, independent of structural details of the guest molecules or properties of the host matrices which, however, had similar clearing temperatures. Alternations in τ for a homologous series of guest molecules are observed. Increasing host permittivity leads to increased values of τ while the viscous properties of the host show little influence on τ.

scholarly journals AC – Conductivity Study of CdSe Nanorods

2018 ◽  
Vol 2 (1) ◽  
Keyword(s):  
Dielectric Relaxation ◽  
Relaxation Times ◽  
Complex Impedance ◽  
Relaxation Mechanism ◽  
Electrical Equivalent Circuit ◽  
Chemical Route ◽  
Polaron Hopping ◽  
Transmission Electron ◽  
Complex Impedance Plane Plot ◽  
Cole Model

The nanorods of cadmium selenide (CdSe) have been synthesized by soft chemical route using mercapto ethanol as a capping agent. The sample forms a rod like shape, confirmed by transmission electron microscope (TEM) measurement. Impedance spectroscopy is applied to investigate the dielectric relaxation of the sample at a various temperature region with varying frequency range. Grain and grain boundary effects both are present in the complex impedance plane plot and is analyzed by an electrical equivalent circuit consisting of a resistance and a constantphase element. Dielectric relaxation mechanism shows peak positions in the imaginary parts of the spectra and that is analyzed by Cole–Cole model. The temperature-dependent relaxation times obeys Arrhenius law having activation energy of 0.391 eV, which indicates that polaron hopping is responsible for conduction or dielectric relaxation in this material. The presence of two plateaus in the frequency-dependent conductivity spectra follows double-power law

Dielectric Relaxation Studies of Silver Nanoparticles dispersed Liquid Crystal

2015 ◽  
Vol 8 (3) ◽  
pp. 2176-2188 ◽  
Author(s):  
Keisham Nanao Singh
Keyword(s):  
Activation Energy ◽  
Silver Nanoparticles ◽  
Liquid Crystal ◽  
Dielectric Relaxation ◽  
Relaxation Process ◽  
Relaxation Times ◽  
Low Frequency ◽  
Bulk Liquid ◽  
Molecular Rearrangement ◽  
Relaxation Studies

This article reports on the Dielectric Relaxation Studies of two Liquid Crystalline compounds - 7O.4 and 7O.6 - doped with dodecanethiol capped Silver Nanoparticles. The liquid crystal molecules are aligned homeotropically using CTAB. The low frequency relaxation process occurring above 1 MHz is fitted to Cole-Cole formula using the software Dielectric Spectra fit. The effect of the Silver Nanoparticles on the molecular dipole dynamics are discussed in terms of the fitted relaxation times, Cole-Cole distribution parameter and activation energy. The study indicate a local molecular rearrangement of the liquid crystal molecules without affecting the order of the bulk liquid crystal molecules but these local molecules surrounding the Silver Nanoparticles do not contribute to the relaxation process in the studied frequency range. The observed effect on activation energy suggests a change in interaction between the nanoparticles/liquid crystal molecules.

Relaxation processes of some simple aliphatic molecules in dilute solutions

1977 ◽  
Vol 55 (4) ◽  
pp. 297-301 ◽  
Author(s):  
M. P. Madan
Keyword(s):  
Carbon Tetrachloride ◽  
Dielectric Relaxation ◽  
Thermodynamic Parameters ◽  
Relaxation Times ◽  
Relaxation Processes ◽  
Dilute Solutions ◽  
Microwave Region ◽  
Nonpolar Solvents ◽  
Dielectric Data ◽  
Intramolecular Rotation

The dielectric relaxation processes of acetone, cyclohexanone, 4-methyl-2-pentanone, and 4-heptanone in dilute nonpolar solvents, n-heptane, cyclohexane, benzene, and carbon tetrachloride have been studied in the microwave region over a temperature range 10 to 60 °C. The relaxation times and the thermodynamic parameters for the activated states have been determined using the measured dielectric data. The results have been discussed in terms of dipole reorientation by molecular and intramolecular rotation and compared, wherever possible, with other similar studies on aliphatic molecules.

scholarly journals Multiscale Post-Seismic Deformation Based on cGNSS Time Series Following the 2015 Lefkas (W. Greece) Mw6.5 Earthquake

2021 ◽  
Vol 11 (11) ◽  
pp. 4817
Author(s):  
Filippos Vallianatos ◽  
Vassilis Sakkas
Keyword(s):  
Time Series ◽  
Relaxation Time ◽  
Relaxation Times ◽  
Relaxation Mechanism ◽  
Mesoscopic Scale ◽  
Macroscopic Scale ◽  
Epicentral Area ◽  
Arrhenius Dependence ◽  
Seismic Deformation ◽  
Logarithmic Type

In the present work, a multiscale post-seismic relaxation mechanism, based on the existence of a distribution in relaxation time, is presented. Assuming an Arrhenius dependence of the relaxation time with uniform distributed activation energy in a mesoscopic scale, a generic logarithmic-type relaxation in a macroscopic scale results. The model was applied in the case of the strong 2015 Lefkas Mw6.5 (W. Greece) earthquake, where continuous GNSS (cGNSS) time series were recorded in a station located in the near vicinity of the epicentral area. The application of the present approach to the Lefkas event fits the observed displacements implied by a distribution of relaxation times in the range τmin ≈3.5 days to τmax ≈350 days.

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