scholarly journals How Ethylene Glycol Chains Enhance the Dielectric Constant of Organic Semiconductors: Molecular Origin and Frequency Dependence

2020 ◽  
Vol 12 (15) ◽  
pp. 17783-17789 ◽  
Author(s):  
Selim Sami ◽  
Riccardo Alessandri ◽  
Ria Broer ◽  
Remco W. A. Havenith
Keyword(s):  
Dielectric Constant ◽  
Ethylene Glycol ◽  
Frequency Dependence ◽  
Organic Semiconductors ◽  
Molecular Origin

scholarly journals An effective strategy to enhance the dielectric constant of organic semiconductors – CPDTTPD-based low bandgap polymers bearing oligo(ethylene glycol) side chains

2018 ◽  
Vol 6 (3) ◽  
pp. 500-511 ◽  
Author(s):  
Jeroen Brebels ◽  
Evgenia Douvogianni ◽  
Dries Devisscher ◽  
Raghavendran Thiruvallur Eachambadi ◽  
Jean Manca ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Ethylene Glycol ◽  
Organic Semiconductors ◽  
Dielectric Constants ◽  
Side Chains ◽  
Effective Strategy ◽  
Low Bandgap

Gradually increasing dielectric constants (up to 6.3) are obtained for a series of PCPDTTPD polymers.

scholarly journals Characterization of percolation behavior in conductor–dielectric 0-3 composites

2014 ◽  
Vol 04 (04) ◽  
pp. 1450035 ◽  
Author(s):  
Lin Zhang ◽  
Patrick Bass ◽  
Zhi-Min Dang ◽  
Z.-Y. Cheng
Keyword(s):  
Dielectric Constant ◽  
Percolation Threshold ◽  
Frequency Dependence ◽  
Experimental Results ◽  
Effective Dielectric Constant ◽  
Filler Concentration ◽  
Percolation Behavior ◽  
The Matrix ◽  
The Relationship

The equation ε eff ∝ (ϕc - ϕ)-s which shows the relationship between effective dielectric constant (εeff) and the filler concentration (φ), is widely used to determine the percolation behavior and obtain parameters, such as percolation threshold φc and the power constant s in conductor–dielectric composites (CDCs). Six different systems of CDCs were used to check the expression by fitting experimental results. It is found that the equation can fit the experimental results at any frequency. However, it is found that the fitting constants do not reflect the real percolation behavior of the composites. It is found that the dielectric constant is strongly dependent on the frequency, which is mainly due to the fact that the frequency dependence of the dielectric constant for the composites close to φc is almost independent of the matrix.

ON THE DIELECTRIC BEHAVIOR OF LiCo3/5Fe2/5VO4 CERAMICS

2010 ◽  
Vol 24 (07) ◽  
pp. 665-670
Author(s):  
MOTI RAM
Keyword(s):  
Activation Energy ◽  
Dielectric Constant ◽  
Frequency Dependence ◽  
Chemical Method ◽  
Arrhenius Plot ◽  
Dielectric Behavior ◽  
Tangent Loss ◽  
Low Frequencies ◽  
Different Temperatures ◽  
Tan Δ

The LiCo 3/5 Fe 2/5 VO 4 ceramics has been fabricated by solution-based chemical method. Frequency dependence of the dielectric constant (εr) at different temperatures exhibits a dispersive behavior at low frequencies. Temperature dependence of εr at different frequencies indicates the dielectric anomalies in εr at Tc (transition temperature) = 190°C, 223°C, 263°C and 283°C with (εr) max ~ 5370, 1976, 690 and 429 for 1, 10, 50 and 100 kHz, respectively. Frequency dependence of tangent loss ( tan δ) at different temperatures indicates the presence of dielectric relaxation in the material. The value of activation energy estimated from the Arrhenius plot of log (τd) with 103/T is ~(0.396 ± 0.012) eV.

Effect of Solvent on Protonation Equilibria of L-Serine and L-Tryptophan in Ethylene Glycol-Water Mixtures

2021 ◽  
Vol 25 (7) ◽  
pp. 124-129
Author(s):  
Ch. Sudhakar ◽  
Allabakshu Shaik ◽  
M. Ramanaiah ◽  
Ch. Nageswara Rao
Keyword(s):  
Dielectric Constant ◽  
Ethylene Glycol ◽  
Protonation Constants ◽  
Statistical Parameters ◽  
Protonation Equilibria ◽  
Effect Of Solvent ◽  
R Factor ◽  
Chemical Models ◽  
Best Fit ◽  
Skewness And Kurtosis

Protonation equilibria of L-serine and L-tryptophan in varying compositions (0.0-50.0 % v/v) of ethylene glycol-water mixtures were investigated pH-metrically. Titrations were performed at 303.0 K and the ionic strength of the medium was maintained at 0.16 mol L-1 using sodium chloride. The protonation constants have been calculated with the computer program MINIQUAD 75 and are selected based on statistical parameters. The best fit chemical models of the protonation equilibria were based on crystallographic R-factor, χ2, skewness and kurtosis. The protonation constants of L-serine and L-tryptophan change linearly with increasing ethylene glycol content. This is attributed to the dielectric constant of the medium.

Radio-wave reflectivity from cold glaciers

2020 ◽  
Author(s):  
Olga Yushkova ◽  
Taisiya Dymova ◽  
Viktor Popovnin
Keyword(s):  
Dielectric Constant ◽  
Dielectric Permittivity ◽  
Reflection Coefficient ◽  
Surface Temperature ◽  
Frequency Dependence ◽  
Depth Profile ◽  
Loss Tangent ◽  
Thin Layers ◽  
The Arctic ◽  
Radio Waves

<p>Radio echo-sounding is a powerful technique for investigating the subsurface of the glaciers. However, physics underlying the formation of the reflected signal is sometimes oversimplified  in the geophysical glacier studies, leading to wrong results. Various remote sensing techniques use different wavelengths (e.g., 13.575 GHz for CryoSat and 20-25/200-600 MHz for ground-penetrating radar), but it is still not clear which particular wavelengths are the best to detect different characteristics of the ice. Possibly, the results gained using different wavelengths may not coincide but rather complement each other due to frequency dependence of the dielectric permittivity and conductivity of snow, ice and especially water.</p><p>Here we attempt to construct an electrophysical model of a cold glacier. This mathematical model considers the variability of the depth profile of the complex dielectric permittivity depending on the frequency of the probing radio signal and the surface temperature. A series of calculations of the reflection coefficients of radio waves from the modelled glacier show that at low temperatures for frequencies above 1 MHz the real part of the dielectric constant of the glacier does not change with frequency and surface temperature, but depends on the glacier structure, while the depth profile of the loss tangent is constant throughout the glacier.  As wavelength decreases, the absorption of radio-waves by the glacier decreases and the frequency dependence of the reflection coefficient becomes a periodic function, its period and amplitude depend on the glacier thickness, the dielectric constant of the bedrock and ice on the surface.</p><p>The range of radio-waves from 0.1 to 1 MHz is not optimal for sounding cold glaciers: the absorption of radio-waves by ice is large for studying thick layers of the glacier, and the wavelength does not allow studying thin layers. Hence, reflection from the glacier surface prevails upon reflection of the signal. The small absorption of short radio waves by ice leads to the fact that the frequency dependence of the reflection coefficient of short radio-waves is practically the sum of the partial reflections of radio-waves from the surface and internal snow/firn and firn/ice boundaries. Period and amplitude of oscillations of the function  depend on the depth of the internal boundaries and the gradient of dielectric characteristics of ice, snow, firn and bedrock.</p><p>Changes in surface temperature, leading to a change in the loss tangent of the upper glacier layers, are manifested in the phase magnitude of the reflection coefficient of radio-waves:it grows with the temperature. Theoretically, the high-frequency signal reflected from the glacier contains information about the structure of the cold glacier and the depth distribution of the dielectric constant, but to restore the electrophysical parameters of the glaciers, it is necessary to use a broadband signal with smooth spectrum and high digitization speed.</p><p>The reported study was funded by RFBR, project number 18-05-60080 (“Dangerous nival-glacial and cryogenic processes and their impact on infrastructure in the Arctic”).</p>

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