Dielectric Relaxation Analysis Research Articles

Dielectric Relaxation Analysis of Water Adsorption in Sol Gel Derived Silica Gel Monoliths

ABSTRACTThe polarization mechanism of the low frequency dielectric relaxation (R1) observed in water adsorbed in porous silica gel is investigated using monolithic samples. It is attributed to electrode polarization involving proton hopping conduction. The influence of the thickness of the adsorbed water layer on the relaxation mechanism is discussed.

Analysis of dielectric relaxations of w/o emulsions in the light of theories of interfacial polarization

An attempt is made to apply dielectric theories of interfacial polarization to observations of dielectric relaxations for W/O emulsions. Approximate formulas for disperse systems in a W/O type were derived from the two theories: one proposed by Maxwell and Wagner for dilute disperse systems of spherical particles, and the other developed by Hanai for concentrated disperse systems. Dielectric measurements were carried out on concentrated W/O emulsions prepared from kerosene and distilled water or KCl aqueous solutions by minimal use of emulsifiers. Marked dielectric relaxations were observed with the emulsions, the dielectric parameters having been determined to characterize the relaxation data. Phase parameters such as relative permittivity, electric conductivity and volume fraction of the disperse phase were evaluated from the dielectric parameters by use of the approximate formulas of the respective theories. The phase parameters evaluated and the frequency dependence of complex permittivity of the W/O emulsions deduced from the theory for concentrated disperse systems are in excellent agreement with the observed data in comparison to that for dilute disperse systems. It is concluded that the dielectric relaxations due to the interfacial polarization of disperse systems of spheres are explained satisfactorily by the theory for concentrated disperse systems.

Evaluation of Relative Permittivity and Electrical Conductivity of Ion-Exchange Beads by Analysis of High-Frequency Dielectric Relaxations

Dielectric measurements on suspensions of an ion-exchange resin, Sephadex G-25, in water, were carried out over the frequency range 30 Hz to 1.7 MHz. The marked dielectric relaxations observed were assigned to interfacial polarization. To evaluate the relative permittivity and electrical conductivity of the dispersed resin beads from the dielectric relaxation data, the observed data were analysed on the basis of two theoretical equations: one proposed by Wagner for dilute disperse systems, and the other derived by Hanai for concentrated disperse systems. The results of this data analysis showed that more suitable values for the relative permittivity and electrical conductivity of the beads in suspension were obtained from Hanai's equations.

A method of analysis of dielectric relaxation: application to a few X zeolites and liquid crystals

The authors have developed a new method of analysis of dielectric spectra showing a distribution of relaxation times. This method, which is founded on modern theories of dielectric relaxation, uses a relation between the complex permittivity and the microscopic autocorrelation function. They give two examples of the application of their method to the analysis of dielectric spectra obtained from porous materials and liquid crystals.

Cole—Cole Diagram and the Distribution of Relaxation Times

The completeness of the Cole—Cole diagram in the analysis of dielectric relaxation is proved by showing explicitly that a semicircle in the Cole—Cole diagram corresponds uniquely to a Debye relaxation function. A method is established to distinguish a continuous distribution of relaxation times from a single relaxation time.