A dielectric permittivity spectrum over a wide range of frequencies. The real and imaginary parts of permittivity are shown, and various processes are depicted: ionic and dipolar relaxation, and atomic and electronic resonances at higher energies.

Dielectric spectroscopy (sometimes called impedance spectroscopy) measures the dielectric properties of a medium as a function of frequency.^[1][2][3][4] It is based on the interaction of an external field with the electric dipole moment of the sample, often expressed by permittivity. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Animation of the dispersion of light as it travels through a triangular prism. ... Electrical impedance, or simply impedance, is a measure of opposition to a sinusoidal alternating electric current. ... A dielectric is a physical model commonly used to describe how an electric field behaves inside a material. ... For other uses, see Frequency (disambiguation). ... Dipole moment refers to the quality of a system to behave like a dipole. ... Permittivity is a physical quantity that describes how an electric field affects and is affected by a dielectric medium and is determined by the ability of a material to polarize in response to an applied electric field, and thereby to cancel, partially, the field inside the material. ...

Dielectric mechanisms

There are a number of different dielectric mechanisms, connected to the way a studied medium reacts to the applied field (see the figure illustration). Each dielectric mechanism is centered around its characteristic frequency, which is the reciprocal of the characteristic time of the process. In general, dielectric mechanisms can be divided into relaxation and resonance processes. The most common, starting from high frequencies, are: The characteristic time of a system is the time it takes for the system to undergo a specific change. ... In physics, dielectric relaxation refers to the relaxation reponse of a dielectric medium to an external field of microwave frequencies. ... This article is about resonance in physics. ...

Electronic polarization

This resonant process occurs in a neutral atom when the electric field displaces the electron density relative to the nucleus it surrounds. Properties For other meanings of Atom, see Atom (disambiguation). ... Electron density is the measure of the probability of an electron being present at a specific location. ... The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ...

This displacement occurs due to the equilibrium between restoration and electric forces.

Atomic polarization

Atomic polarization is observed when the electronic cloud is deformed under the force of the applied field, so that the negative and positive charge are formed. This is a resonant process.

Dipole relaxation

This originates from permanent and induced dipoles aligning to an electric field. Their orientation polarisation is disturbed by thermal noise (which mis-aligns the dipole vectors from the direction of the field), and the time needed for dipoles to relax is determined by the local viscosity. These two facts make dipole relaxation heavily dependent on temperature and chemical surrounding. The Earths magnetic field, which is approximately a dipole. ... For other uses, see Viscosity (disambiguation). ... For other uses, see Temperature (disambiguation). ...

Ionic relaxation

Ionic relaxation comprises ionic conductivity and interfacial and space charge relaxation. Ionic conductivity predominates at low frequencies and introduces only losses to the system. Interfacial relaxation occurs when charge carriers are trapped at interfaces of heterogeneous systems. Ionic conduction in solids has been a subject of interest for as early as the beginning of the 19th century. ...

Dielectric relaxation

Dielectric relaxation as a whole is the result of the movement of dipoles (dipole relaxation) and electric charges (ionic relaxation) due to an applied alternating field, and is usually observed in the frequency range 10²-10¹⁰ Hz. Relaxation mechanisms are relatively slow compared to resonant electronic transitions or molecular vibrations, which usually have frequencies above 10¹² Hz. In physics, dielectric relaxation refers to the relaxation reponse of a dielectric medium to an external field of microwave frequencies. ...

References

1. ^ Kremer F., Schonhals A., Luck W. Broadband Dielectric Spectroscopy. – Springer-Verlag, 2002.
2. ^ Sidorovich A. M., Dielectric Spectrum of Water. – Ukrainian Physical Journal, 1984, vol. 29, No 8, p. 1175-1181 (In Russian).
3. ^ Hippel A. R. Dielectrics and Waves. – N. Y.: John Willey & Sons, 1954.
4. ^ Volkov A. A., Prokhorov A. S., Broadband Dielectric Spectroscopy of Solids. – Radiophysics and Quantum Electronics, 2003, vol. 46, Issue 8, p. 657–665.

See also

• Debye relaxation
• Dielectric dispersion
• Dielectric function
• Dipole
• Permittivity