scholarly journals Static and Dynamic Dielectric Properties of Mesogenic n-Nonyloxycyanobiphenyl (9OCB)

2007 ◽  
Vol 62 (1-2) ◽  
pp. 61-66
Author(s):  
Grzegorz Czechowski ◽  
Jan Jadżyn
Keyword(s):  
Activation Energy ◽  
Phase Transitions ◽  
Dielectric Properties ◽  
Dielectric Relaxation ◽  
Rotational Diffusion ◽  
Short Axis ◽  
Frequency Range ◽  
Static Permittivity ◽  
Anomalous Temperature ◽  
Smectic A

The dielectric properties of n-nonyloxycyanobiphenyl in the isotropic (I), nematic (N) and smectic A (SA) phases were investigated. The dielectric relaxation spectra, recorded in the frequency range 50 kHz - 100 MHz, were analyzed with use of the Cole-Cole equation. An anomalous temperature behavior of the static permittivity, the rotational diffusion exponent and the activation energy of mesogenic molecules rotating around their short axis, observed in the vicinity of the phase transitions, are discussed.

scholarly journals Dielectric and Conduction Processes and Behaviours in Ni0.3Zn0.7Fe2O4

2016 ◽  
Vol 846 ◽  
pp. 311-317
Author(s):  
Mohd Noor Mat ◽  
M.K. Halimah ◽  
Wan Mohd Daud Wan Yusoff ◽  
H. Mansor ◽  
H. Nizam ◽  
...  
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
Iron Oxide ◽  
Dielectric Properties ◽  
Dielectric Relaxation ◽  
Relaxation Process ◽  
Peak Frequency ◽  
Frequency Range ◽  
Dielectric Relaxation Process ◽  
Frequency Relaxation

Dielectric relaxation and conductivity of Ni0.3Zn0.7Fe2O4 (NZF) were studied in the frequency range between 0.01 Hz to 3 MHz and temperature range within 313 K to 473 K. The sample was prepared by mixing Zinc Oxide, Nickel Oxide and Iron Oxide and sintered at 1573 K for 10 hours long. Dielectric properties were studied using Novo Control Dielectric Spectrometer. Dielectric relaxation and conductivity phenomena were discussed using an empirical model to key out the dielectric relaxation process. Analyze peak frequency relaxation process consist of four slopes to explain the dielectric relaxation process. The conductivity of the sample indicates an activated process and activation energy of dc conductivity is 0.44 ± 0.01 eV.

scholarly journals Dielectric Properties of Deep Ice Cores with Air-Hydrate Inclusions (Abstract)

1988 ◽  
Vol 10 ◽  
pp. 210
Author(s):  
Shinji Mae ◽  
Takeo Hondoh ◽  
Masayoshi Nakawo ◽  
C.C. Langway
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
Dielectric Properties ◽  
Time Variation ◽  
Volume Fraction ◽  
Ice Cores ◽  
Frequency Range ◽  
Temperature Range ◽  
The Core

Air-hydrate inclusions have been found in deep ice cores from Dye 3, Greenland, which were taken in August 1981. Although the concentration of the air-hydrate crystals decreased with time, when the core was stored at a temperature of −50 °C, they still existed to an appreciable extent in 1985. An ice specimen was cut out from the Dye 3 core at a depth of 1500 m, where the volume fraction of the hydrate crystals was about 10−3 by volume. Its dielectric properties were measured in September 1985, in a frequency range of 30-20 × 103 Hz and temperature range of −20° to −90°C. The activation energy obtained for the relaxation time of the Debye dispersion was about 0.2 eV, which is much smaller than that of pure ice. The measurement was repeated once a month for about a year, and the sample was stored at a temperature of −10 °C between measurements. The time variation of the dielectric properties has been discussed in relation to the deterioration of the air-hydrate crystals.

Dielectric relaxation of nonionic microemulsion: influence of the salinity

2001 ◽  
Vol 79 (1) ◽  
pp. 49-58
Author(s):  
G Delbos ◽  
M Keita ◽  
T K Bose
Keyword(s):  
Dielectric Properties ◽  
Dielectric Relaxation ◽  
Relaxation Frequency ◽  
The Other ◽  
Spectral Amplitude ◽  
Microemulsion System ◽  
Frequency Range ◽  
Amplitude Increase ◽  
Nacl Concentration ◽  
Main Relaxation

Study of dielectric properties of a quaternary microemulsion system composed of water, oil, a nonionic surfactant, and an alcohol, in the frequency range 100 kHz – 15 GHz is reported as a function of salt (NaCl) concentration. Depending on the salinity, the decomposition of the dielectric spectra shows the presence of two or three main relaxation domains. The lower relaxation frequency and the corresponding spectral amplitude increase as a function of salinity. The other observed relaxation mechanisms are shown to be dipolar in origin.PACS No.: 97.22Gn

scholarly journals Dielectric Behaviour of Disperse Ice Microcrystals in The Frequency Range 105 to 10-2 Hz

1978 ◽  
Vol 20 (83) ◽  
pp. 359-365
Author(s):  
C. Lafargue ◽  
C. Bourgeois ◽  
G. Evrard
Keyword(s):  
Activation Energy ◽  
Dielectric Properties ◽  
Activation Energies ◽  
Dielectric Behaviour ◽  
Ageing Effect ◽  
Frequency Range ◽  
Low Frequencies

AbstractDielectric properties of ice microcrystals have been studied in the frequency range 3 x 105 to 10-2 Hz. Two separated dispersions are revealed : the Debye dispersion of ice and another dispersion at very low frequencies. Both dispersions present an ageing effect, with decreasing activation energy for the Debye dispersion and with increasing activation energy for the second one. It is shown in this paper that the sum of these activation energies retains a constant value of (1.05±0.02) eV.

Dielectric relaxation of lithium and sodium perchlorates in 1,2-dimethoxyethane and propylene carbonate

1981 ◽  
Vol 59 (7) ◽  
pp. 1051-1060 ◽  
Author(s):  
Hubert Cachet ◽  
Mohamed Fekir ◽  
Jean-Claude Lestrade
Keyword(s):  
Dielectric Properties ◽  
Ethyl Acetate ◽  
Dielectric Relaxation ◽  
Propylene Carbonate ◽  
Complex Permittivity ◽  
Ion Pairs ◽  
Conductivity Measurements ◽  
Frequency Range ◽  
Dielectric Data

The complex permittivity of LiClO4 and NaClO4 solutions in 1,2-dimethoxyethane (DME) has been measured in the frequency range 0.140–123.2 GHz. The data have been analysed according to a model for the reorientation of ion pairs given in a previous paper. The dielectric data are supplemented by conductivity measurements in a broad concentration range (10−4–1 mol/L) which evidence the large extent of salt association. The main result is that the solvation of Li+ and Na+ by DME cannot be described as simply as in the case of other solvents, such as tetrahydrofuran or ethyl acetate, as far as the dielectric properties are concerned: while the assumption of rigidly bound solvating molecules was acceptable for the latter solvents, some freedom in the reorientation of these molecules has to be taken into account for the case of DME. LiClO4 solutions in propylene carbonate (PC) + benzene and PC + DME mixtures have also been studied. The data, for the latter, can be qualitatively interpreted under the assumption that PC molecules take the place of DME molecules in the solvation sheath, even at low PC concentration.

scholarly journals Dielectric Properties of Deep Ice Cores with Air-Hydrate Inclusions (Abstract)

1988 ◽  
Vol 10 ◽  
pp. 210-210
Author(s):  
Shinji Mae ◽  
Takeo Hondoh ◽  
Masayoshi Nakawo ◽  
C.C. Langway
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
Dielectric Properties ◽  
Time Variation ◽  
Volume Fraction ◽  
Ice Cores ◽  
Frequency Range ◽  
Temperature Range ◽  
The Core

Air-hydrate inclusions have been found in deep ice cores from Dye 3, Greenland, which were taken in August 1981. Although the concentration of the air-hydrate crystals decreased with time, when the core was stored at a temperature of −50 °C, they still existed to an appreciable extent in 1985.An ice specimen was cut out from the Dye 3 core at a depth of 1500 m, where the volume fraction of the hydrate crystals was about 10−3 by volume. Its dielectric properties were measured in September 1985, in a frequency range of 30-20 × 103 Hz and temperature range of −20° to −90°C. The activation energy obtained for the relaxation time of the Debye dispersion was about 0.2 eV, which is much smaller than that of pure ice.The measurement was repeated once a month for about a year, and the sample was stored at a temperature of −10 °C between measurements. The time variation of the dielectric properties has been discussed in relation to the deterioration of the air-hydrate crystals.

DIELECTRIC PROPERTIES OF POLYVINYL ACETALS

1952 ◽  
Vol 30 (12) ◽  
pp. 940-947 ◽  
Author(s):  
B. L. Funt ◽  
T. H. Sutherland
Keyword(s):  
Dielectric Properties ◽  
Electrical Properties ◽  
Dielectric Relaxation ◽  
Relaxation Times ◽  
Dielectric Dispersion ◽  
Transition Temperatures ◽  
Free Energies ◽  
Frequency Range ◽  
Physical Picture ◽  
Electrical Relaxation

Measurements of dielectric dispersion in vinyl acetal and formal polymers were performed over the frequency range 0.050 to 100 kc. at temperatures between 25 and 135 °C. The results reflect the effects of internal plasticization on the electrical properties of the polymers. With increasing size of the substituent groups from formal to butyral the dispersion range is shifted to lower temperatures at a given frequency. Electrical relaxation times and transition temperatures were obtained and values of enthalpies, free energies, and entropies of activation were calculated. A tentative physical picture of the mechanism of dielectric relaxation in these polymers was also formulated.

scholarly journals Dielectric Behaviour of Disperse Ice Microcrystals in The Frequency Range 105 to 10-2 Hz

1978 ◽  
Vol 20 (83) ◽  
pp. 359-365 ◽  
Author(s):  
C. Lafargue ◽  
C. Bourgeois ◽  
G. Evrard
Keyword(s):  
Activation Energy ◽  
Dielectric Properties ◽  
Activation Energies ◽  
Dielectric Behaviour ◽  
Ageing Effect ◽  
Frequency Range ◽  
Low Frequencies

Abstract Dielectric properties of ice microcrystals have been studied in the frequency range 3 x 105 to 10-2 Hz. Two separated dispersions are revealed : the Debye dispersion of ice and another dispersion at very low frequencies. Both dispersions present an ageing effect, with decreasing activation energy for the Debye dispersion and with increasing activation energy for the second one. It is shown in this paper that the sum of these activation energies retains a constant value of (1.05±0.02) eV.

scholarly journals Phase Diagram and Dielectric Relaxation Studies of n-Hexyl-isothiocyanato-biphenyl (6BT) in the Smectic E Phase under High Pressure

2002 ◽  
Vol 57 (5) ◽  
pp. 233-236 ◽  
Author(s):  
Stanislaw Urban ◽  
Albert Würflinger
Keyword(s):  
Phase Diagram ◽  
Dielectric Relaxation ◽  
Liquid Crystalline ◽  
Activation Volume ◽  
Activation Enthalpy ◽  
Temperature Phase ◽  
Short Axis ◽  
Frequency Range ◽  
Relaxation Measurements ◽  
Analogous Data

The pressure-temperature phase diagram of n-hexyl-isothiocyanato-biphenyl (6BT) at up to 190 MPa and 250 - 400 K was established with the aid of DTA. The dielectric relaxation measurements in the SmE phase of 6BT were performed in the pressure range of 0.1 - 150 MPa and the temperature range of 320 - 350 K. The Debye-type relaxation process was observed in the frequency range of 100 Hz - 100 kHz. The longitudinal relaxation time characterizing the molecular reorientations around the short axis was analyzed with respect to the pressure and temperature dependencies, yielding the activation volume, Δ#V = RΤ(∂ ln τ/∂p)Τ , and activation enthalpy, Δ#H = R(∂ ln τ/∂Τ-1)p , respectively. The results are compared with the analogous data obtained recently for 8BT and other similar compounds having the nematic and SmA liquid crystalline phases.in the telluride retain their molecular character, with small intercluster interactions.

LOW TEMPERATURE STUDIES OF THE DIELECTRIC AND ELECTRICAL PARAMETERS OF GLASSY Se90Ge10-xInx

2002 ◽  
Vol 09 (03n04) ◽  
pp. 1379-1385
Author(s):  
S. ABOU EL-HASSAN
Keyword(s):  
Activation Energy ◽  
Dielectric Properties ◽  
Low Temperature ◽  
Localized States ◽  
Frequency Range ◽  
Electrical Parameters ◽  
Cbh Model ◽  
Correlated Barrier Hopping ◽  
Density Of Localized States ◽  
Different Temperatures

The dielectric properties of the system Se 90 Ge 10-x In x (x = 2, 4 and 6 at. %) were studied in the temperature range of 78–273 K and in the frequency range of 400 Hz–20 kHz. The density of localized states N(E) and the activation energy of hopping wk for the samples were deduced at different temperatures. The exponents s, m1 and m2 of the equations σ ac (ω) = Aωs, ε′ = Bωm1 and ε′′ = Cωm2 have been deduced for the samples. The composition and temperature dependence of s, m1, m2, wk and N(E) have been determined. The results are interpreted in terms of the correlated barrier hopping (CBH) model and the concept of localized states.

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