DIELECTRIC PROPERTIES OF DRY, GEOLOGIC MATERIALS

Geophysics ◽  
1970 ◽  
Vol 35 (4) ◽  
pp. 624-645 ◽  
Author(s):  
M. Saint‐Amant ◽  
David W. Strangway
Keyword(s):  
Dielectric Properties ◽  
Loss Tangent ◽  
Relaxation Times ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Relaxation Peak ◽  
Debye Relaxation ◽  
Thermally Activated ◽  
Geologic Materials ◽  
Frequency Independent

A detailed investigation of the dielectric properties of powdered and solid dry rocks in the frequency range of 50 hz to 2 mhz has revealed the following general characteristics: 1) All dry rocks, powdered and solid, show an increase in both the dielectric constant and the loss tangent as frequency decreases and as temperature increases. This dispersion is believed to be due to polarization associated with charge buildup at grain boundaries or at grain imperfections. 2) Dry powdered rocks often show a thermally‐activated relaxation peak with a typical Debye‐relaxation character. This is due to the presence of pyroxene and biotite and may be associated with other minerals. The relaxation peak is not seen in solid rocks, where it is hidden by the low‐frequency dispersion. 3) At high frequencies, the loss tangent approaches a constant value which is frequency independent. This behavior is observed in many dielectrics and may be the result of a distribution of relaxation times.

High-Temperature Dielectric Properties of Goethite From 400 to 3000 MHz

2005 ◽  
Vol 20 (1) ◽  
pp. 18-29 ◽  
Author(s):  
C.A. Pickles ◽  
J. Mouris ◽  
R.M. Hutcheon
Keyword(s):  
Dielectric Properties ◽  
Thermogravimetric Analysis ◽  
Perturbation Technique ◽  
Relaxation Times ◽  
Relaxation Processes ◽  
Heating Rates ◽  
Hydrogen Atoms ◽  
Debye Relaxation ◽  
The Real ◽  
Thermally Activated

The dielectric properties of goethite and, in particular, the changes during the topotactic conversion of goethite to hematite were studied from room temperature to about 800 °C in the frequency range of 400 to 3000 MHz using the cavity perturbation technique. The complex permittivity, that is, both the real and the imaginary or absorptive parts (έ and ἕ), were measured under various heating regimens. In addition, thermogravimetric analysis (TGA) was performed to characterize the transformation of goethite to hematite. The Debye relaxation formalism was applied to the processes occurring both during and after the main dehydroxylation reaction to calculate the relaxation times. The Arrhenius equation for thermally activated relaxation times was used to determine the activation energies. Both the real and the absorptive parts of the permittivity exhibited a significant peak during the main part of the goethite to hematite decomposition reaction. Above the transformation, there was another, less dramatic, thermally activated increase in the permittivity values. The increase in the permittivities during the goethite to hematite transformation was attributed to the formation of quasi-free migrating radicals, for example, hydroxyl ions, oxygen ions, or hydrogen atoms, during the dehydroxylation of goethite. The derivative thermogravimetric analysis (DTGA) curve was found to be directly related to the transient values of the real and the imaginary permittivities. Higher heating rates resulted in an accelerated rate of dehydroxylation and therefore higher values of the transient permittivities. In the temperature range of 400 °C to 500 °C (i.e., just above the dehydroxylation peak), the real permittivity exhibited a varying frequency dependence, which suggested that changes were occurring in the newly formed, highly defected hematite structure, which is referred to as hydrohematite. During the reaction there were multiple relaxation processes and thus the Debye relationship could not be applied. However, at temperatures above about 500 °C, the structure stabilized, the Debye relationship was more closely followed, and the relaxation times could be determined as a function of temperature. The activation energy for the relaxation process above 500 °C was determined to be 0.47 kJ/mol.

Synthesis and dielectric properties of tungsten-based complex perovskites

2003 ◽  
Vol 18 (11) ◽  
pp. 2600-2607 ◽  
Author(s):  
D.D. Khalyavin ◽  
Jiaping Han ◽  
A.M.R Senos ◽  
P.Q. Mantas
Keyword(s):  
Dielectric Properties ◽  
Temperature Variation ◽  
Single Phase ◽  
Low Frequency ◽  
Double Perovskites ◽  
Dielectric Measurements ◽  
Anomalous Temperature ◽  
Conventional Solid State Reaction ◽  
Thermally Activated ◽  
Second Phases

Ba2MeWO6 (Me=Mg, Ni, Zn) double perovskites were prepared by the conventional solid-state reaction in a wide temperature range. Single-phase ceramics were obtained only at low temperatures approximately 1200°C, whereas a small amount of second phases existed in the samples sintered at higher temperatures. All the compounds are characterized by the cubic perovskite structure (space group Fm3m) with a complete NaCl type ordering between B-site ions. Anomalous temperature variation of the dielectric loss tangent found in the Ba2NiWO6 perovskite is supposed to be connected with a dielectric relaxation due to electronic hopping within thermally activated Ni3+-6W(6-1/6)+/W5+-6Ni(2+1/6)+ clusters. Dielectric measurements showed that the other two perovskites—Ba2ZnWO6 and Ba2MgWO6—exhibit a positive value of the temperature coefficient of permittivity. Such temperature variation is assumed to be caused by a considerable influence of the second polar mode involving B-site ion vibrations on the low-frequency dielectric properties.

The dielectric properties of aqueous nucleic acid solutions

1966 ◽  
Vol 291 (1426) ◽  
pp. 368-388 ◽  
Keyword(s):  
Dielectric Properties ◽  
High Frequency ◽  
Deoxyribonucleic Acid ◽  
General Pattern ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Theoretical Interpretation ◽  
Acid Solutions ◽  
Dispersion Region ◽  
Ionic Polarization

The dielectric properties of aqueous solutions of the sodium salts of ribonucleic acid and deoxyribonucleic acid have been determined. The general pattern of behaviour observed for other aqueous polyelectrolyte systems has been verified in these studies. There are indications that a low frequency dispersion region (below 2 Mc/s) is present as well as the normal high frequency dispersion region. The theoretical interpretation of the experimental results makes use of the O’Konski theory of ionic polarization and the formulation of an equilibrium between counterions ‘non-specifically bound’ and ‘free’ from the electrostatic field of the polyion. Calculations are made on the basis of this theory and estimates of the values of the specific conductivities existing at the polyion surface are made.

THE DIELECTRIC PROPERTIES OF SELECTED BASALTS

Geophysics ◽  
1973 ◽  
Vol 38 (1) ◽  
pp. 135-139 ◽  
Author(s):  
W. Hansen ◽  
W. R. Sill ◽  
S. H. Ward
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Loss Tangent ◽  
Room Temperature ◽  
Frequency Dispersion ◽  
Nitrogen Atmosphere ◽  
Frequency Range ◽  
Dielectric Constant And Loss ◽  
Identical Composition ◽  
Titanium Compounds

Basaltic samples of known chemical composition were measured for dielectric constant and loss tangent in the frequency range 100 hz to 50 Mhz. All samples were prepared and measured by a contact substitution method in a dry nitrogen atmosphere at room temperature. The measurements indicated a general spectrum of dielectric constant with a range of 10–65 at 100 hz to 7–15 at 50 Mhz with frequency dispersion observed to be minimal above 1 Mhz. The loss tangent decreases from a range .2–.9 at 100 hz to a range .02–.15 at 100 khz. A finer‐grained sample was observed to have higher dielectric properties below 1 Mhz than a coarser‐grained sample of identical composition. A qualitative and subsequent quantitative study of possible compositional effects indicated that iron‐titanium compounds may be responsible for observed variations in the dielectric spectra of typical basalts.

Influence of Iodine on Low Frequency Dielectric Properties of Anthrone

1995 ◽  
Vol 60 (11) ◽  
pp. 1809-1814
Author(s):  
Grzegorz W. Bak ◽  
Marian Kryszewski
Keyword(s):  
Charge Transfer ◽  
Dielectric Properties ◽  
Dielectric Response ◽  
Charge Transfer Complex ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Low Loss ◽  
Remarkable Change ◽  
Ct Complex

Low frequency dielectric properties of polycrystalline anthrone and anthrone/iodine charge-transfer complex are presented. Polycrystalline anthrone proves to be a typical low-loss material. Iodization of anthrone pellets leads to a remarkable change in dielectric properties. Dielectric response of anthrone/iodine CT complex shows comparatively strong low frequency dispersion. The change in dielectric properties proves to be reversible to great extend as removing of iodine by heating at 373 K for a few hours almost completely restores the dielectric values of a virgin anthrone sample.

Zur Deutung der kernmagnetischen Relaxation in Proteinlösungen

1970 ◽  
Vol 25 (11) ◽  
pp. 1680-1684 ◽  
Author(s):  
R. Kimmich ◽  
F. Noack
Keyword(s):  
Relaxation Time ◽  
High Frequency ◽  
Relaxation Times ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Proton Relaxation ◽  
Protein Solutions ◽  
Longitudinal Relaxation Time ◽  
Two Phase ◽  
Protein Molecules

Abstract Measurements of longitudinal and transversal proton relaxation times in both H2O and mixed H2O/D2O protein solutions show a low-frequency as well as a high-frequency dispersion of the longitudinal relaxation time and a nonexponential two-phase transversal relaxation. These results are discussed qualitatively in terms of “rigid” and “mobile” relaxation centers within the protein molecules.

Dielectric Behavior of CVD (Ba,Sr)TiO3 thin Films on Pt/Si

1995 ◽  
Vol 415 ◽  
Author(s):  
S.K. Streiffer ◽  
C. Basceri ◽  
A.I. Kingon ◽  
S. Lipa ◽  
S. Bilodeau ◽  
...  
Keyword(s):  
Thin Films ◽  
Carrier Transport ◽  
Low Frequency ◽  
Chemical Vapor ◽  
Frequency Dispersion ◽  
Dielectric Behavior ◽  
Polarization Current ◽  
Low Dissipation ◽  
Frequency Independent ◽  
The Time Domain

ABSTRACTWe have investigated the dielectric behavior of polycrystalline (Ba,Sr)TiO3 thin films deposited by liquid-source metalorganic chemical vapor deposition. The time-domain polarization current, the frequency dependence of the permittivity, and the dielectric loss for these CVD films are all described by a single set of parameters via the phenomenology of Curie - von Schweidler behavior. No change in the general form of the permittivity is found out to 1.5 GHz, suggesting that this description of the response is valid into the frequency range of interest for many applications. Low-frequency dispersion is found to be controllable, leading to films with very low dissipation factors and almost frequency-independent dielectric response. Finally, a non-zero intercept of the inverse of capacitance versus film thickness suggests the existence of a series interfacial capacitance, arising from either microstructural inhomogeneity or energy barriers to carrier transport at the film-electrode interfaces.

Complex Dielectric Spectroscopy Characterization of a Li0.982Ta1.004O3 Ferroelectric Single Crystal

1997 ◽  
Vol 500 ◽  
Author(s):  
Ming Dong ◽  
Rosario A. Gerhardt
Keyword(s):  
Dielectric Properties ◽  
Single Crystal ◽  
Measurement Data ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Nonlinear Least Squares ◽  
Electrical Measurement ◽  
Ferroelectric Single Crystal ◽  
Crystal Bulk

ABSTRACTThe dielectric properties of a c-oriented ferroelectric Li0.982Ta1.004O3 single crystal have been investigated. The frequency and the temperature dependence of the dielectric properties have been measured from 500 to 650°C at frequencies ranging from 5 to 106 Hz. Both blocking and non-blocking electrodes were used for separating the electrode effect from the crystal bulk dielectric response. A low-frequency dispersion was identified to be due to the contribution of Li+ ionic carriers. Based on the electrical measurement data and complex nonlinear least squares fitting, an equivalent circuit is proposed to represent the dielectric properties of the single crystal.

scholarly journals Frequency and temperature dependent transport properties of NiCuZn ceramic oxide

2015 ◽  
Vol 33 (2) ◽  
pp. 259-267 ◽  
Author(s):  
M. Belal Hossen ◽  
A.K.M. Akther Hossain
Keyword(s):  
Dielectric Properties ◽  
Low Frequency ◽  
Interfacial Polarization ◽  
Polycrystalline Sample ◽  
Phenomenological Theory ◽  
Sintered Sample ◽  
Solid State Reaction Method ◽  
Complex Dielectric Constant ◽  
Ceramic Oxide ◽  
Frequency Independent

AbstractA polycrystalline sample of ceramic oxide Ni0.27Cu0.10Zn0.63Fe2O4 was prepared by the solid state reaction method. The sintered sample was well polished to remove any oxide layer formed during sintering and the two surfaces of the pellet were coated with a silver paste as a contact material. Among dielectric properties, complex dielectric constant (ε* = εʹ - jεʺ), loss tangent (tanδ) and ac conductivity (σac) in the frequency range of 20 Hz to 2 MHz were analyzed in the temperature range of 303 to 498 K using a Wayne Kerr impedance analyzer (model No. 6500B). The experimental results indicate that ε, εʺ, tanδ and σac decrease with an increase in frequency and increase with increasing temperature. The transition temperature, as obtained from dispersion curve of εʹ, shifts towards higher temperature with an increase in frequency. The variation of dielectric properties with frequency and temperature shows the dispersion behavior which is explained in the light of Maxwell-Wagner type of interfacial polarization in accordance with the Koop’s phenomenological theory. The frequency dependent conductivity results satisfy the Jonscher’s power law, σT(ω) = σ(o)+Aωn, and the results show the occurrence of two types of conduction process at elevated temperature: (i) low frequency conductivity, due to long-range ordering (frequency independent, region I), (ii) mid frequency conductivity at the grain boundaries (region II, dispersion) and (iii) high frequency conductivity at the grain interior due to the short-range hopping mechanism (frequency independent plateau, region III).

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