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1.
Dielectric relaxation study of N,N-dimethylformamide (DMF) has been carried out with propylene glycol (PLG) at different temperatures. Time domain reflectometry (TDR) in reflection mode has been used to measure the reflection coefficient in frequency range of 10 MHz to 20 GHz. The dielectric parameters static dielectric permittivity (? 0) and relaxation time (τ) have been obtained by Fourier transform and least squares fit methods. The experimental results show nonlinear variation in dielectric permittivity and relaxation time with volume fraction of PLG confirm the structural formation due to the intermolecular interaction between N,N-dimethylformamide and PLG. The variation in excess permittivity (ε E), excess inverse relaxation times (1/τ)E, Kirkwood correlation factors (g eff, g f), activation enthalpy (ΔH) and entropy (ΔS) are also calculated to study the binary mixture interaction. 相似文献
2.
S. N. Migunov A. A. Volkov G. A. Komandin A. N. Lobanov B. P. Gorshunov Yu. I. Golovko V. M. Mukhortov Yu. I. Yuzyuk 《Technical Physics》2008,53(11):1485-1489
Using submillimeter and infrared spectroscopies, the reflectance R(ν) and transmittance T(ν) spectra of heteroepitaxial barium-strontium titanate films of different thicknesses on MgO substrates are taken for the
first time in the frequency range 10 < ν < 3000 cm−1. By modeling the experimental spectra by the Fresnel formulas for layered media, the spectra of complex permittivity ɛ*(ν)
= ɛ′(ν) + iɛ″(ν) of the films are determined. It is shown that when the film thicknesses decrease down to 10 nm, there appear tensile
stresses in the direction parallel to the substrate surface. As a result, the dielectric contribution of a low-frequency soft
mode becomes several times larger than before. 相似文献
3.
CdS nanoparticles have been synthesized by a chemical reaction route using thiophenol as a capping agent. The frequency-dependent
dielectric dispersion of cadmium sulphide (CdS) is investigated in the temperature range of 303-413 K and in a frequency range
of 50 Hz-1 MHz by impedance spectroscopy. An analysis of the complex permittivity (ɛ′ and ɛ″) and loss tangent (tan δ) with frequency is performed by assuming a distribution of relaxation times. The scaling behaviour of dielectric loss spectra
suggests that the relaxation describes the same mechanism at various temperatures. The frequency-dependent electrical data
are analysed in the framework of conductivity and modulus formalisms. The frequency-dependent conductivity spectra obey the
power law. 相似文献
4.
The densities (α) and ultrasonic velocities (C) of binary mixtures of a polar liquid like acetone and toluene have been measured at different frequencies (lMHz, 3MHz and
5MHz) over the entire range of mole fraction of acetone at temperature 303.16k. The intermolecular free length (L
f
), isentropic compressibility (β), acoustic impedance (Z), excess values of isentropic compressibility (β
E
) and acoustic impedance (Z
E
) have been computed using values of ultrasonic velocity (C) and density (α). The ultrasonic velocity (C), intermolecular free length (L
f
) and excess values of isentropic compressibility are positive whereas excess values of acoustic impedance is negative for
the entire composition range which indicates the specific interaction between unlike molecules. The results are discussed
in the light of intermolecular interactions occurring in the solutions. 相似文献
5.
The densities (ρ) and ultrasonic velocities (C) of binary mixture of diisopropyl ether (DIPE) and bromobenzene (BB) have been measured at different frequencies (1 MHz,
3 MHz and 5 MHz) over the entire range of mole fraction of diisopropyl ether (DIPE) at temperature 303 K. The intermolecular
free length (L
f
), isentropic compressibility (β), acoustic impedance (Z) and excess values of isentropic compressibility (β
E
) and acoustic impedance (ZE) have been computed using values of ultrasonic velocity (C) and density (ρ).
The ultrasonic velocity, intermolecular free length are positive whereas the excess values of isentropic compressibility and
acoustic impedance are negative over the entire composition range of DIPE which indicates presence of specific interactions
between unlike molecules. The results are discussed in the light of intermolecular interactions occurring in the mixtures.
相似文献
6.
The dielectric behavior of stearic acid in 1,4-dioxane medium at various temperature 303 K–288 K and frequency regime (10 MHz–30 GHz) determined from the complex dielectric permittivity spectra obtained by Time Domain Reflectometry(TDR). In this frequency range, the dielectric study gives the electrostatic interaction as well as orientational polarizability of complex mixtures of long chain molecules significantly. Dielectric parameters were calculated from the complex spectra of the binary mixture by non linear least square fit method. The excess permittivity (εE), correlation factors were calculated for the binary system. Thermal parameters(ΔH-enthalpy, ΔS-entropy and ΔG-Gibbs free energy) were calculated and the direction of reaction is determined. The FTIR spectrum of the binary system recorded and the assignments are discussed. The FTIR spectral assignments confirm the molecular interactions. 相似文献
7.
The dielectric relaxation parameters, viz., static dielectric constant, ɛ, and relaxation times, τ, have been determined for chlorobenzene-methanol (CB-MET), 1,2 dichloro ethanemethanol (DE-MET) and dimethylene chloride-methanol
(DC-MET) mixtures with thirteen different concentrations at three temperatures, viz., 15, 25 and 45°C. The experimental technique
used for this work was the time domain reflectometry (TDR) in the frequency range of 10 MHz to 20 GHz using the Hewlett Packard
HP 54750 sampling oscilloscope. The information regarding hydrogen bonding structural behavior in MET due to CB, DE and DC
are obtained by using the theoretical models based on the excess properties. The data suggest that CB and DE are not influenced
by hydrogen bonding in MET whereas DC is influenced by the hydrogen bonding mechanism in MET. It appears that the behavior
of DC on MET is different from CB and DE in MET. 相似文献
8.
L.S. GabrielyanS.A. Markarian 《Journal of Molecular Liquids》2011,162(3):135-140
The complex dielectric spectra of dipropylsulfoxide (DPSO)/water mixtures in the whole concentration range have been measured as a function of frequency between 100 MHz and 20 GHz at four temperatures between 298.15 K and 328.15 K. The dielectric parameters, static dielectric constant (εs), relaxation time (τ) and relaxation strength (Δε) have been obtained by the least squares fit method. The relaxation in these mixtures can be described by two Debye functions, whereas for pure DPSO Cole-Davidson type is valid. The relaxation times of the mixtures show a maximum at about x(DPSO) ≈ 0.3. In the concentration range where a maximum appears, the interaction of DPSO with water is presumably the result of hydrogen bonding between water and the sulfonyl group of the sulfoxide molecule. The concentration and temperature dependent excess dielectric constant and effective Kirkwood correlation factor of the binary mixtures have been determined. The excess permittivity is found to be negative for all concentrations. 相似文献
9.
High-quality YBaCuO films are used to sequentially prepare a 10-GHz disk resonator and a planar inductance coil. The Q factor
of the planar inductance coil at its resonance frequency (64 MHz) is much higher than the values reported for analogous structures.
The measurement results are used to estimate the surface resistance of the films at frequencies of 10 GHz and 64 MHz. The
surface resistance measured at 64 MHz is more than fourfold of that calculated from the surface resistance measured at 10
GHz by the dependence R
sur ∼ ω2. Our analysis demonstrates that extrinsic factors cannot substantially affect the measurement results; therefore, the deviation
from the R
sur ∼ ω2 dependence in the megahertz range is determined by the intrinsic properties of the superconducting strip. 相似文献
10.
Fannin PC Malaescu I Marin CN Stefu N 《The European physical journal. E, Soft matter》2008,27(2):145-148
This paper reports on the frequency dependence of the magnetic and electric power dissipation in a magnetic fluid sample,
in the microwave frequency range (0.5 to 8GHz), at various values of the static magnetic field (0 to 167.8kA/m). The computation
of the power dissipation relies on the experimental values measured for the complex dielectric permittivity, ɛ = ɛ′ - iɛ″, and the complex magnetic permeability, μ = μ′ - iμ″, over the same frequency range. The results show that the magnetic power dissipation is much larger than the electric one
for the investigated sample. At a specific frequency, f (Hz) , the power dissipation, p, depends on the external magnetic field, and exhibits a maximum. The result obtained suggests the possibility of controlling
the energy absorption in the microwave range by means of the application of an external magnetic field. 相似文献
11.
The complex permittivity (ɛ = ɛ′ − iɛ″) of natural, modified, and irradiated zeolites as a function of the frequency of a variable electric field is measured.
For Ba2+-modified (doped) zeolite, the permittivity and dielectric loss tangent (tanδ) as functions of the electric field frequency
are found to decrease monotonically. When the irradiation dose rises to 105 cm−2, the dielectric loss tangent reaches a maximum and then, starting from a dose of 3 × 1016 cm−2, sharply drops. Such behavior of tanδ is assumed to be associated with Ba2+- and irradiation-induced structural modifications in the unit cell of zeolite. 相似文献
12.
The effect of gamma irradiation on the dielectric properties and ac conductivity of a TlInS2 single crystal with a layered structure has been investigated in the frequency range from 5 × 104 to 3.5 × 107Hz. It has been shown that gamma irradiation of the TlInS2 single crystal with a dose of 104–2.25 × 106 rad leads to a considerable increase in the dielectric loss tangent tanδ, the real part ɛ′ and imaginary part ɛ″ of the complex
permittivity, and the ac conductivity σ
ac
across the layers. It has been established that, for all gamma irradiation doses, the TlInS2 single crystal is characterized by the dielectric loss due to electrical conduction up to a frequency of 107 Hz and by the relaxation loss at a higher frequency. Irradiation of the TlInS2 single crystal results in an increase in the dispersion of tan δ, ɛ′, and ɛ″. It has been demonstrated that, as the gamma
irradiation dose is accumulated in the TlInS2 single crystal, the density of localized states near the Fermi level N
F increases (from 5.2 × 1018 to 1.9 × 1019 eV−1 cm−3). 相似文献
13.
M. D. Volnyanskii S. N. Plyaka M. P. Trubitsyn Yahia A. H. Obaidat 《Physics of the Solid State》2012,54(3):499-503
The electrical properties of a lithium heptagermanate (Li2Ge7O15) crystal have been studied in DC and AC measuring fields at temperatures from 500 to 700 K. In a DC field, a substantial
decrease of electrical conductivity σ with time has been detected. On the basis of kinetic dependences σ(t), estimates of the charge carrier diffusion coefficient D have been obtained. In the frequency range 101–105 Hz, the spectra of complex impedance ρ*(f) have been measured. The analysis of diagrams in the complex plane (ρ″–ρ′) has been performed within the equivalent circuit
approach. It has been shown that, in the considered temperature and frequency intervals, the electrical properties of Li2Ge7O15 crystals have been determined by the hopping conduction of interstitial lithium ions A
Li and accumulation of charge carriers near the blocking Pt electrodes. 相似文献
14.
The Ac electrical conductivity and the dielectric relaxation properties of the [(C3H7)4N]2Cd2Cl6 polycrystalline sample have been investigated by means of impedance spectroscopy measurements over a wide range of frequencies
and temperatures, 209 Hz–5 MHz and 361–418 K, respectively. The purpose is to make a difference between the electrical and
dielectric properties of the polycrystalline sample and single crystal. Besides, a detailed analysis of the impedance spectrum
suggests that the electrical properties of the material are strongly temperature-dependent. Plots of (Z" versus Z') are well
fitted to an equivalent circuit model consisting of a series combination of grains and grains boundary elements. Moreover,
the temperature dependence of the electrical conductivity in the different phases follows the Arrhenius law and the frequency
dependence of σ (ω) follows the Jonscher’s universal dynamic law. Furthermore, the modulus plots can be characterized by full
width at half height or in terms of a nonexperiential decay function φ(t) = exp(t/t)β. Finally, the imaginary part of the permittivity constant is analyzed with the Cole–Cole formalism. 相似文献
15.
The relaxor ferroelectric lead iron tantalate, Pb(Fe0.5Ta0.5)O3 (PFT) is synthesized by Coulombite precursor method. The X-ray diffraction pattern of the sample at room temperature shows
a cubic phase. The field dependence of dielectric response is measured in a frequency range 0.1 kHz — 1 MHz and in a temperature
range from 173–373 K. The temperature dependence of permittivity (ɛ′) shows broad maxima at various frequencies. The frequency dependence of the permittivity maximum temperature (T
m
) has been modelled using Vogel-Fulcher relation.
相似文献
16.
S. V. Demishev A. V. Semeno N. E. Sluchanko N. A. Samarin I. B. Voskoboinikov M. V. Kartsovnik A. E. Kovalev N. D. Kushch 《Journal of Experimental and Theoretical Physics》1997,84(3):540-544
Resonant microwave absorption in a (BEDO-TTF)2ReO4(H2O) organic conductor single crystal at a temperature of 1.9 K, a magnetic field of up to 70 kOe, and in the frequency band
between 30 and 120 GHz has been studied. A spectral component due to the cyclotron resonance (CR) of two-dimensional charge
carriers has been identified for ν⩾80 GHz and H⩾10 kOe. The effective mass m(ω) increases with the frequency from m≈0.8m
0 at ν=80 GHz to m≈0.95m
0 at ν=120 GHz. Measurements of the CR line position and FWHM as functions of frequency yield an independently determined imaginary
part of the memory function M(ω), which controls the dynamic magnetoconductivity, and the relaxation time τ(ν=100 GHz)≈2.9×10−11 s, which is more than thirty times the value of this parameter in the low-frequency limit τ(ν→0). The anomalous behavior of the CR line position and FWHM is caused by the dispersion of both real and imaginary parts
of M(ω), which are probably due to strong Fermi-liquid effects.
Zh. éksp. Teor. Fiz. 111, 979–987 (March 1997) 相似文献
17.
The complex permittivity spectra for tert-butyl alcohol (TB) with 2-propanol (2P) were determined over the frequency range of 10 MHz to 20 GHz using the time domain reflectometry (TDR) in the temperature range 25 °C to 55 °C for 11 different concentrations of the system. The static dielectric constant (ε0) and relaxation time (τ) have been determined these spectra using the Debye model. Excess properties and Kirkwood correlation factor of the mixtures have been determined. The excess permittivity is found to be positive in the tert-butyl alcohol rich region and negative in the 2-propanol rich region. However, the excess inverse relaxation time has different trend. The static dielectric constants for the mixtures have also been fitted with the modified Bruggeman model by assuming an additional parameter in the model. It appears that structure of the TB–2P dimer in the TB rich region favors parallel dipole orientation, whereas in the 2P rich region, it favors antiparallel orientation. 相似文献
18.
Summary The relaxation processes of glass-forming polymethylacrylate have been studied in a wide temperature range above the glass
transition temperatureT
g by means of light scattering measurements. Experimental spectra give evidence of a self-similar behaviourI(ω) ∝ ω−(1−a) over a spectral range of 2–3 decades, consistent with the predictions of the mode-coupling theory. Different from the prediction
of the theory, the value ofa is strongly temperature dependent. This behaviour has been attributed to the presence of a slow secondary relaxation located
in the GHz frequency region, whose strength progressively increases with temperature.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献
19.
A. U. Sheleg V. G. Hurtavy S. N. Mustafaeva E. M. Kerimova 《Physics of the Solid State》2011,53(3):472-475
The temperature dependences of the electrical conductivity and the permittivity of TlInSe2 and TlGaTe2 crystals unirradiated and irradiated with 4-MeV electrons at a doze of 1016 cm−2 have been investigated. It has been established that electron irradiation leads to a decrease in the electrical conductivity
σ and the permittivity ɛ over the entire temperature range under study (90–320 K). It has been revealed that the TlInSe2 and TlGaTe2 single crystals undergo a sequence of phase transitions characteristic of crystals of this type, which manifest themselves
as anomalies in the temperature dependences σ = f(T) and ɛ = f(T). Electron irradiation at a doze of 1016 cm−2 does not affect the phase transition temperatures of the crystals under investigation. 相似文献
20.
The behavior of the impedance spectra of island permalloy films prepared through vacuum evaporation onto optically polished
glass-ceramic substrates has been investigated in the frequency range from 0.0001 to 100 MHz. A resistor-capacitor model of
the films has been developed and the model parameters, for which there is a good agreement with experimental data on the frequency
dependences of the real and imaginary components of the impedance, have been determined. The specific features in the behavior
of the electrical and physical characteristics with variations in the thickness of the sample and the gap between the measuring
electrodes have been investigated. It has been found that the relative permittivity of the films under investigation reaches
values ɛ ∼ 107–108. The structural relaxation times have been calculated. 相似文献