Dielectric Relaxation Spectroscopy DRS

The electrolyte solution is stimulated by an electromagnetic field applied over the microwave region, and the dielectric response of the sample is then measured. The complex dielectric response is frequency sensitive and dependent on the square of the dipole moment of each species in solution. Both solvent molecules and dipolar ion-pairs contribute to the signal. Additional contributions arise from the polarizability 

On the other hand DRS is complex and fraught with potential problems, for example, under the effect of the applied field, there is ionic migration and the ionic conductivity term must be deconvolved from the dipolar response at lower frequencies. Moreover DRS is technologically demanding and expensive and only well trained personnel can exploit its potential [99,100]. 

A number of studies have been carried out of the glass transition process using dielectric relaxation spectroscopy. With the advent of computer-assisted measurements the DRS technique has increased in popularity and is now routinely used for the study of molecular mobility in polymeric materials. Chemical bonds may possess dipole moments as a consequence of the dilferences in 

The dielectric relaxation experiment can be visualized in terms of a simple capacitor in which the dipoles are aligned by an applied electric field ( ). The magnitude of the charge-displacement field that is observed on the plates depends on the polarizability of the media between the plates of the capacitor. The greater the polarizability the larger the charge that can be carried by the plates. The polarization (P) induced per unit volume for a material placed between parallel plates in a capacitor can be related to the susceptibility % of the material to be polarized  

In a simple experiment removal of the applied field allows the polarization in the capacitor to decay as a consequence of the randomization of the dipoles. The decay will be determined by a relaxation time x. The decay of the polarization in the capacitor can be described by 

As in the case of the dynamic mechanical experiment we are dealing with mathematical complex quantities. The dielectric permittivity should be 

The angular frequency m dependence of the complex permittivity can be described by 

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Smith et al. [1.127] reviewed the dielectric relaxation spectroscopy (DRS) as a method for structural characterization of polymers and proteins providing, among others, information about the water content and states of water. 

In Chapter 7, Mano and Dionisio describe how electrical methods, and particularly dielectric relaxation spectroscopy (DRS) and thermally stimulated depolarisation current (TSDS) techniques, play a major role as tools for e2q)loring molecular mobility. DRS enables molecular relaxational processes (both slow and fast) to be studied. For example, the localized motions of glass formers in the glassy state give rise to local fluctuations of the dipole vector that are the origin of the secondary relaxation processes detected by dielectric relaxation spectroscopy, while above, but near, the glass transition, cooperative motions result in a distinguishably different relaxation process (the a-relaxation). 

Dielectric relaxation spectroscopy (DRS) was used for studies of the effects of confinement, the type and concentration of clay, and the molecular weight of... 

Dielectric Relaxation Spectroscopy - [DRS]. Isothermal and isochronal ageing studies were carried out over a frequency range from 10 to 6.5 x 10 Hz at 10 C temperature intervals between 30-120 C (13). 

Table 142 Structural properties of ASD measurable by dielectric relaxation spectroscopy (DRS) and possible hurdles... 

Figure 6.11. Block diagram of the components of the instrumentation, and their interconnection, typically used for dielectric relaxation spectroscopy (DRS) studies.

In this paper, we review our experimental and simulation work [5-7] and include new results on the solid - liquid phase behavior of mixtures confined in nanopores. Dielectric relaxation spectroscopy (DRS) was used to study the experimental phase diagram of CClVCaHn mixtures confined in activated carbon fibers (ACF). Grand Canonical Monte Carlo (GCMC) simulations with the parallel tempering technique were used to model the freezing of Lennard-Jones mixtures in slit pores. Mixtures having a simple solid solution or... 

Properties such as formation of ion pairs, viscosity, conductivity, and mobility are important factors to describe the efficiency of ion transport. Dielectric relaxation spectroscopy (DRS) [529] is a method that has not been applied for studying electrolytes related to lithium ion batteries. This group anticipates that this situation... 

Phase structure and relaxation behavior. In previous publications [38,40,43-49], several methods were used for characterization of the microphase structure of the semi-IPNs studied. WAXS, SAXS, DSC [40], dielectric relaxation spectroscopy (DRS), and TSDC [48] measurements showed that pure PCN is characterized by a typical homogeneous structure, but in segmented TPUs microphase separation was observed on the level of the thermodynamically immiscible hard and soft domains. As for semi-IPNs, the destruction of the microphase-separated morphology of TPU was observed and microphase separation between the PCN and TPU phases, expected from the difference in their solubility parameters, was not found. Grigoryeva et al. [43] noted that... 

In most cases, the measurements are carried out isothermally in the frequency domain and the terms dielectric spectroscopy (DS) and dielectric relaxation spectroscopy (DRS) are then used. Other terms frequently used for DRS are impedance spectroscopy and admittance spectroscopy. Impedance spectroscopy is usually used in connection with electrolytes and electrochemical studies, whereas admittance spectroscopy often refers to semiconductors and devices. Isothermal measurements in the time domain are often used, either as a convenient tool for extending the range of measurements to low frequencies (slow time-domain spectroscopy, dc transient current method, isothermal charging-discharging current measurements) or for fast measurements corresponding to the frequency range of about 10 MHz - 10 GHz (time-domain spectroscopy or time-domain reflectometry). Finally, TSDC is a special dielectric technique in the temperature domain, which will be discussed in Section 2.2. 

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