Maxwell-Wagner polarisations

Another type of polarization arises from a charge build-up in the contact areas or interfaces between different components in heterogeneous systems. This phenomenon is also known as interfacial polarization and is due to the difference in the conductivities and dielectric constants (see below) of the materials at interfaces. The accumulation of space charge is responsible for field distortions and dielectric loss and is commonly termed Maxwell-Wagner polarisation . 

The impedance spectrum of the RF aerogels in the density range of 340 kgW up to 880 kg/m is clearly dominated by losses due to relaxation processes. Considering the so called Maxwell-Wagner polarisation we were able to attribute these losses to adsorbed water layers. 

Keywords aerogels, dielectric permittivity, response function, impedance spectrum, Maxwell-Wagner polarisation... 

The macroscopically observed transport is based on the quantum-mechanical interaction between the electron waves in neighbouring quantum metal particles , which is probably facilitated by the Maxwell-Wagner polarisation and thermally stimulated. Instead of hopping , the expression tunnelling may approximate more closely to the quantum mechanical fundamentals of this process. 

In heterogeneous systems, an interfacial polarisation is Created due to the space charges. This polarisation corresponds to the electron motion inside conductive charges, dispersed in an insulated matrice (Maxwell-Wagner Model). In fact, this phenomenon will appear as soon as two materials I and 2 are mixed so that c7]/ei C2le.2 with a conductivity and e dielectric constant at zero frequency [ 123]. 

The value of e" polarisation is related to the molecular polarisation phenomena such as dipole rotation (Debye model), space charge relaxation (Maxwell-Wagner model), hopping of confined charges [42,126,127]. The physical origin of this polarisation term is often ambiguous [42],... 

As its name implies, interfacial polarisation (IP) arises from mobile charges piling up at interfaces in a material. For example, the N-layer Maxwell-Wagner (MW) capacitor... 

We come now to a quite different form of polarisation, although once again charge is trapped at the extremities of dipolar entities. This is the electrical effect when a discontinuous conducting phase is dispersed in a continuous insulating phase. The phenomenon was studied first by Maxwell, and then by Wagner, and most recently by SiUars. So, for polymer systems, it is called Maxwell—Wagner— SiUars polarisation. 

A third relaxation type mechanism, which once again hsis its strongest influence in the radio frequency range, is a loss due to space charges in interfaces between different dielectric materials, referred to as Maxwell-Wagner loss. It may be assumed that at the low frequencies where these losses are important, the conductivity loss mechanism referred to above will be the dominant one for ceramic materials and therefore losses due to Maxwel1-Wagner polarisation will not be considered any further. 

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