In dielectric spectroscopy, large frequency dependent contributions to the dielectric response, especially at low frequencies, may come from build-ups of charge.
This Maxwell–Wagner–Sillars polarization (or often just Maxwell–Wagner polarization), occurs either at inner dielectric boundary layers on a mesoscopic scale, or at the external electrode-sample interface on a macroscopic scale.
In both cases this leads to a separation of charges (such as through a depletion layer).
The charges are often separated over a considerable distance (relative to the atomic and molecular sizes), and the contribution to dielectric loss can therefore be orders of magnitude larger than the dielectric response due to molecular fluctuations.
[1] It is named after the works of James Clerk Maxwell (1891), Karl Willy Wagner (1914) and R. W. Sillars (1937).
[2] Maxwell-Wagner polarization processes should be taken into account during the investigation of inhomogeneous materials like suspensions or colloids, biological materials, phase separated polymers, blends, and crystalline or liquid crystalline polymers.
[3] The simplest model for describing an inhomogeneous structure is a double layer arrangement, where each layer is characterized by its permittivity
Importantly, since the materials' conductivities are in general frequency dependent, this shows that the double layer composite generally has a frequency dependent relaxation time even if the individual layers are characterized by frequency independent permittivities.
A more sophisticated model for treating interfacial polarization was developed by Maxwell [citation needed], and later generalized by Wagner [4] and Sillars.
[5] Maxwell considered a spherical particle with a dielectric permittivity
suspended in an infinite medium characterized by
Certain European text books will represent the