Dielectric Relaxation Spectroscopy

Wróbel, S.; Gestblom, Bo; Jadżyn, Jan; Kędziora, P.; Hellemans, Louis; Würflinger, A.; Urban, S.

doi:10.1007/978-3-662-09747-2_2

Cited by 16 publications

(5 citation statements)

References 176 publications

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“…Starting from the Debye function, several formulas for both the frequency and the time domain have been suggested to describe the experimentally observed spectra. The most important approaches are discussed below [97,98]. a. Debye model: It is a method to study the dielectric behaviour of a material by measuring the complex dielectric permittivity versus frequency at constant temperature and ambient pressure.…”

Section: Macroscopic Models For Dielectric Spectramentioning

confidence: 99%

An Overview of Polymer-Dispersed Liquid Crystals Composite Films and Their Applications

Katariya-Jain¹,

Deshmukh²

2020

Liquid Crystals and Display Technology

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Inherent and incredible properties of liquid crystals (LC) such as optical and dielectric anisotropy make them special candidates for flat-panel display devices; bi-stable reflective displays; high-definition spatial light modulators; switchable windows; haze-free normal-and reverse-mode light shutter devices; projectors; optical, thermal and strain sensors; tuneable lenses; etc. Non-linear response of LC material to the applied electric field is very useful in the above-mentioned applications. When a low molecular weight LC material is doped in a high molecular weight polymer matrix to obtain polymer-dispersed liquid crystal (PDLC) films, it offers flexibility and mechanical strength (structural stabilization) to the composite films-PDLC devices. Depending upon the concentration of monomer/polymer, these composite films are classified as polymer-stabilized liquid crystal (PSLC), PDLC and holographic PDLC (HPDLC) films. Depending upon the process conditions, we get phase-separated randomly dispersed micron-sized LC droplets in a continuous polymer matrix. These nematic LC droplets exhibit light scattering transmission properties depending on their orientation, which can be controlled by external electric field. This chapter gives deep insight about operating principle, phase separation techniques involved, alignment of LC and controlling LC droplet morphology of PDLC films to obtain desired properties. In order to improve the optical efficiency and to obtain the desired result from PDLC films, various guest entities such as dye and nanomaterials are doped in the host LC material. This chapter also accounts for various possible LC dopants desired for improving the electro-optic (EO) and dielectric properties of PDLC devices. Various applications of PDLC composite films are also described in this chapter.

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Section: Macroscopic Models For Dielectric Spectramentioning

confidence: 99%

An Overview of Polymer-Dispersed Liquid Crystals Composite Films and Their Applications

Katariya-Jain¹,

Deshmukh²

2020

Liquid Crystals and Display Technology

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“…Dielectric researches are one of the most effective methods for the revealing of peculiarities in the structure of two-component heterogeneous systems and the relation of this structure with the mechanisms of formation of the conductivity in those systems [38][39][40]. In particular, the results of corresponding researches make it possible to analyze the manifestations of the effects associated with the formation of transient phases different by their physical properties from the initial components of composites [30,32,37,38].…”

Section: Spectra Of the Dielectric Permittivity Of Composites In The mentioning

confidence: 99%

“…The arrangement of the corresponding region of the dielectric permittivity dispersion can be determined from the dispersion frequency . In the framework of the model, in which the matrix contains Wagner spherical conducting inclusions [40], we have…”

Section: Spectra Of the Dielectric Permittivity Of Composites In The mentioning

confidence: 99%

ize Effects in Electrical Properties of Carbon-Polypropylene Composites

Тонкошкур¹,

Lyashkov²,

Degtyaryov³

2016

Ukr. J. Phys.

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PACS 72.80. Le, 82.35.Np The temperature dependences of the resistance, current-voltage characteristics, and dielectric spectra of composites based on polypropylene and fillers made of micro-and nano-sized carbon particles have been studied. A reduction in the average size of conducting filler particles is found to decrease the resistivity magnitude, to shift the posistor section in the current-voltage characteristics toward lower electric fields and larger currents, and to increase the low-frequency dielectric permittivity of the researched composites. It is shown that these "size"effects can be explained by a growth of the effective fraction of the volume occupied by the conducting filler owing to the emergence of interfacial boundary layers in the polypropylene matrix. The electric properties of the layers differ from those for bulk polyethylene, and charge carriers can move in them. In other words, a change in the size of carbon particles gives rise to changes in the specific area and the effective fraction of the conducting filler.K e y w o r d s: composite, carbon filler, conductivity, dielectric permittivity, interphase layer.

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“…The dielectric relaxation spectroscopy is one of the most effective and popular methods for investigation of inhomogeneous solids (Jonscher, 1990; Kremer and Schönhals, 2003; Wróbel et al , 2003; Belovickis et al , 2015; Said et al , 2016) and disperse liquid and liquid-crystal systems (Cirkel et al , 1997; Barbero and Alexe-Ionescu, 2005; Barsoukov and Macdonald, 2005). In recent years, the materials and structures of modern electronics, in particular varistor (Glot et al , 1979; Han et al , 2003; Fernández-Hevia et al , 2004; Cheng et al , 2008, 2012; Tsonos et al , 2011), capacitor (Cheng et al , 2014; Jana et al , 2014; Löhnert et al , 2015) and gas-sensitive (Ponce et al , 2009; Lyashkov et al , 2013; Morozov et al , 2014) ceramics, polymer composites with a wide spectrum of fillers from carbon black to semiconductors (Sun et al , 2005; Degtyar’ov et al , 2006; Shin and Kwon, 2011; Nuzhnyy et al , 2013; Panda et al , 2014; Kolbunоv et al , 2015), occupy among them a special place.…”

Section: Introductionmentioning

confidence: 99%

Basic models in dielectric spectroscopy of heterogeneous materials with semiconductor inclusions

Тонкошкур

Glot

Иванченко

2017

MMMS

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Purpose The purpose of this paper is to develop the models of the dielectric permittivity dispersion of heterogeneous systems based on semiconductors to a level that would allow to apply effectively the method of broadband dielectric spectroscopy for the study of electronic processes in ceramic and composite materials. Design/methodology/approach The new approach for determining the complex dielectric permittivity of heterogeneous systems with semiconductor particles is used. It includes finding the analytical expression of the effective dielectric permittivity of the separate semiconductor particle of spherical shape. This approach takes into account the polarization of the free charge carriers in this particle, including capturing to localized electron states. This enabled the authors to use the known equations for complex dielectric permittivity of two-component matrix systems and statistical mixtures. Findings The presented dispersion equations establish the relationship between the parameters of the dielectric spectrum and electronic processes in the structures like semiconductor particles in a dielectric matrix in a wide frequency range. Conditions of manifestation and location of the different dispersion regions of the complex dielectric heterogeneous systems based on semiconductors in the frequency axis and their features are established. The most high-frequency dispersion region corresponds to the separation of free charge carriers at polarization. After this region in the direction of reducing of the frequency, the dispersion regions caused by recharge bulk and/or surface localized states follow. The most low-frequency dispersion region is caused by recharging electron traps in the boundary layer of the dielectric matrix. Originality/value Dielectric dispersion models are developed that are associated with: electronic processes of separation of free charge carriers in the semiconductor component, recapture of free charge carriers in the localized electronic states in bulk and on the surface of the semiconductor and also boundary layers of the dielectric at the polarization. The authors have analyzed to situations that correspond applicable and promising materials: varistor ceramics and composite structure with conductive and semiconductor fillers. The modelling results correspond to the existing level of understanding of the electron phenomena in matrix systems and statistical mixtures based on semiconductors. It allows to raise efficiency of research and control properties of heterogeneous materials by dielectric spectroscopy.

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Dielectric Relaxation Spectroscopy

Cited by 16 publications

References 176 publications

An Overview of Polymer-Dispersed Liquid Crystals Composite Films and Their Applications

An Overview of Polymer-Dispersed Liquid Crystals Composite Films and Their Applications

ize Effects in Electrical Properties of Carbon-Polypropylene Composites

Basic models in dielectric spectroscopy of heterogeneous materials with semiconductor inclusions

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