Dielectric dispersion and relaxation mechanism in some trichloro esters at microwave frequencies

1977 ◽  
Vol 55 (21) ◽  
pp. 1902-1905 ◽  
Author(s):  
H. D. Purohit ◽  
H. S. Sharma ◽  
A. D. Vyas
Keyword(s):  
Relaxation Time ◽  
Dielectric Loss ◽  
Weight Fraction ◽  
Relaxation Mechanism ◽  
Dielectric Dispersion ◽  
Relaxation Processes ◽  
Optical Frequency ◽  
Microwave Frequencies ◽  
Group Rotation ◽  
Straight Lines

The permittivity and dielectric loss of three trichloro esters, namely methyl trichloroacetate, ethyl trichloroacetate, and n-propyl trichloroacetate have been measured at frequencies 1 MHz, 9.83, 18.26, 24.50 GHz, and optical frequency at 35 °C. The permittivity and dielectric loss at different frequencies have been plotted against concentration (weight fraction). The slopes of these straight lines have been used for complex plane plots (a″ vs. a′). There are two possible relaxation processes in these molecules, i.e. overall rotation of the molecule and intramolecular group rotation —CCl3 around C—C bond. Whereas the relaxation time for overall rotation is dependent on temperature the relaxation time for group rotation is practically independent of temperature.

Dielectric Dispersion Studies of Some Intramolecular Hydrogen Bonded Molecules at Microwave Frequencies

1977 ◽  
Vol 32 (6) ◽  
pp. 604-606 ◽  
Author(s):  
H. D. Purohit ◽  
S. Kumar ◽  
A. D. Vyas
Keyword(s):  
Dielectric Loss ◽  
Complex Plane ◽  
Dipole Moments ◽  
Dielectric Dispersion ◽  
Dielectric Relaxation Time ◽  
Relaxation Processes ◽  
Microwave Frequencies ◽  
Group Rotation ◽  
Intramolecular Hydrogen ◽  
Straight Lines

Abstract The permittivity and dielectric loss of acetyl acetone, benzoyl acetone and dibenzoyl methane have been measured at four microwave frequencies viz., 30.20, 24.50, 18.26, and 9.83 GHz and also at 1 MHz and optical frequency at 35 °C. The permittivity and dielectric loss at different frequen­ cies have been plotted against concentration (wt. fraction). The slopes of these straight lines have been used for the complex plane plots (a″ vs. a′). The complex plane plots for these compounds are Cole-Cole arcs. The dielectric relaxation time (τ0) and distribution parameter (α) have been calculated from these plots. Data have been analysed in terms of two relaxation processes i. e., cor­ responding to overall rotation and group rotation. The dipole moments of these molecules are reported.

Intramolecular Rotation in Some Trihalogenated Esters at Microwave Frequencies

1978 ◽  
Vol 33 (2) ◽  
pp. 232-234 ◽  
Author(s):  
H. D. Purohit ◽  
A. D. Vyas ◽  
H. C. Lunker
Keyword(s):  
Dielectric Loss ◽  
Complex Plane ◽  
Dispersion Curves ◽  
Relaxation Processes ◽  
Optical Frequency ◽  
Methyl Ethyl ◽  
Microwave Frequencies ◽  
Group Rotation ◽  
Straight Lines ◽  
Intramolecular Rotation

The permittivity and dielectric loss of methyl, ethyl and n-propyl trichloroacetate in decalin solution have been measured at four microwave frequencies viz., 30.20, 24.50, 18.26 and 9.83 GHz and also at 1 MHz and optical frequency at 35 °C. The permittivity and dielectric loss at different frequencies have been plotted against concentration (wt. fraction). The slopes of these straight lines have been used for complex plane plots (a″ vs a′). The dispersion curves which could not be resolved in benzene could be resolved in decalin due to the increase in viscosity of the solvent. Data have been analysed in terms of two relaxation processes i.e., overall rotation and group rotation.

On the Dislocation Contribution to the Dielectric Loss in the Materials with Piezoelectric Properties

2019 ◽  
Vol 945 ◽  
pp. 796-800
Author(s):  
V.N. Nechaev ◽  
V.V. Dezhin
Keyword(s):  
Dielectric Loss ◽  
Electric Field ◽  
Piezoelectric Properties ◽  
Dielectric Dispersion ◽  
Field Energy ◽  
Relaxation Processes ◽  
Variable Electric Field ◽  
Additional Information ◽  
Piezoelectric Coupling ◽  
Energy Dissipated

A variable electric field is applied to a crystal. This field gives rise – through the piezoelectric coupling – to the variable mechanical stresses. Then the dislocations in the crystal will be driven by Peach-Koehler force and will start moving, dissipating the external field energy. Connection of the electric field energy dissipated per unit time with the internal friction is found. The case of resonant loss (Granato-Lucke model) is considered. The loss related to this mechanism to be at frequencies of megahertz range. The relaxation processes being responsible for the Bordoni and Hasiguti peaks also are considered. The use of obtained equations makes it possible to distinguish the dislocation contribution to both dielectric loss and dielectric dispersion and, therefore, to derive additional information about the crystal structure in a sufficiently simple way in terms of only one method.

Theory of the width of the ferromagnetic resonance line of europium iron garnet

1975 ◽  
Vol 344 (1636) ◽  
pp. 21-50 ◽  
Keyword(s):  
Relaxation Time ◽  
Ferromagnetic Resonance ◽  
Resonance Line ◽  
Equations Of Motion ◽  
Dynamic Parameter ◽  
Relaxation Mechanism ◽  
Relaxation Processes ◽  
Anisotropic Exchange ◽  
Temperature Operating ◽  
Iron Garnet

A successful theory of the width of the ferromagnetic resonance line of Eu iron garnet must explain its variation with temperature, operating frequency and direction. It is found that this goal can be achieved by using the so-called ‘ longitudinal ’ theory in which the width is caused by the fact that the population redistribution among the components of J = 1 lags behind the values appropriate to instantaneous equilibrium with the r.f. field. Agreement with experiment requires that the relaxation processes responsible for the redistribution be primarily of the ‘ inter ’ rather than ‘in tra’ type, i.e. associated with transitions between the states J = 0 and J = 1 of the Eu 3+ ion, rather than being internal to J = 1. The mathematical theory is closely related to that of an earlier paper by two of the authors on the static (i.e. free energy) anisotropy of Eu i.g. in that it involves the simultaneous consideration of the crystalline field and anisotropic exchange. Numerical values of the relevant constants are employed which are consistent with those in the earlier paper. Anisotropic exchange is less important relative to the crystalline potential than it was there, but nevertheless improves the agreement with experiment. The present problem requires in addition a dynamic parameter connected with the relaxation rate. The necessary relaxation time is short and has to be about the same for all components of J = 1. The latter requirement is shown to preclude the relaxation mechanism being that of phonon modulation of exchange interaction. The final part of the paper is concerned with the equations of motion relating to the relaxation process. Their solution shows that rigorously there is more than one relaxation time, but the theory based on a single such time is found to be a good approximation in some cases.

Dielectric studies. Part XXV. Methoxy group rotation in anisole and three para-substituted anisoles

1969 ◽  
Vol 47 (24) ◽  
pp. 4645-4650 ◽  
Author(s):  
D. B. Farmer ◽  
S. Walker
Keyword(s):  
Relaxation Process ◽  
Methoxy Group ◽  
Relaxation Times ◽  
Pure Liquid ◽  
Relaxation Processes ◽  
Molecular Relaxation ◽  
Microwave Frequencies ◽  
Dielectric Absorption ◽  
Weight Factors ◽  
Group Rotation

The dielectric absorption at several microwave frequencies of anisole, p-methylanisole, and p-bromoanisole in the solvent p-xylene, and p-dimethoxybenzene in the solvent cyclohexane has been investigated at 4 to 6 temperatures. Anisole, p-methylanisole, and p-dimethoxybenzene were all found to relax mainly by methoxy group rotation, whereas the relaxation process in p-bromoanisole was very largely molecular relaxation. In the literature, considerable divergence exists for the analyses of the dielectric data of anisole and substituted anisoles into contributions from two relaxation times and the magnitude of the weight factors governing each relaxation process. Such divergencies have been explored and justifiable analyses established for these systems where the weight factors governing the relaxation processes are shown to be roughly of the same order as those estimated from group moment data. The weight factor for molecular relaxation in the pure liquid appears considerably greater than that for a dilute solution of it in a non-polar solvent.

scholarly journals Complex dielectric behavior of doped polyaniline conducting polymer at microwave frequencies using time domain reflectometry

2019 ◽  
Vol 65 (6 Nov-Dec) ◽  
pp. 590 ◽  
Author(s):  
D.R. Bijwe ◽  
S.S. Yawale ◽  
A.C. Kumbharkhane ◽  
H. Peng ◽  
D.S. Yawale ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Conducting Polymer ◽  
Chemical Oxidation ◽  
Ammonia Solution ◽  
Dielectric Behavior ◽  
Time Domain Reflectometry ◽  
Microwave Frequencies ◽  
Absorbing Property

Nano size Tin Oxide is prepared in the laboratory from SnCl4 and ammonia solution. The polyaniline (PAni) conducting polymer is synthesized by chemical oxidation method using ammonium persulphate as oxidizing agent. The PAni-SnO2 composite was prepared by insitu method. Scanning electron microscopy (SEM) results confirm the particle size of SnO2 in the range of 30-48 nm.   Dielectric  behavior  of  nanocomposite  of  PAni-SnO2 was  studied  in the frequency range 0.01- 20 GHz at -5,0,5,10,15,20 and  25oC. The dielectric constant (real part ε׳) and dielectric loss (imaginary part ε״) have been evaluated. The relaxation time (τ, τo, and τ1) are calculated. The relaxation time was found to be of the order of ps. The dielectric properties of the solids in the form of powders may be useful in understanding the structural behavior of particles in an alternating field. These studies may also be used to formulate models for predicting the dielectric properties. The microwave absorbing property is decided from the dielectric loss of the material. It is observed that the PAni-SnO2 composite can be a good electromagnetic shielding material.

Asymetric Dielectric Dispersionin Glycols

1977 ◽  
Vol 32 (11) ◽  
pp. 1309-1312 ◽  
Author(s):  
B. S. Rajyam ◽  
C. V. Rama Sastry ◽  
C. R. K. Murty
Keyword(s):  
Relaxation Time ◽  
Diethylene Glycol ◽  
Dielectric Dispersion ◽  
Pure Liquid ◽  
Hydroxyl Groups ◽  
Microwave Frequencies ◽  
Dispersion Data ◽  
Asymmetric Behaviour ◽  
Glycol Solution ◽  
Butane Diol

Abstract Dielectric dispersion studies of two pure liquid glycols, diethylene glycol and 1,3-butane diol, and of 2,2-dimethyl 1,3-propane diol dissolved in dioxane, have been carried out at radio, ultrahigh and microwave frequencies at 30 °C. The dispersion nature of the two pure liquids and the solution conforms to the Cole-Davidson type. The dispersion data on the glycol solution show a significant asymmetric behaviour. Comparison of the dispersion parameter β, and relaxation time τ0 , of the present glycols with those of other glycols reveals that both β and τ0 increase with the number of intervening carbon atoms between the two hydroxyl groups.

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