Effect of Moisture on Low Frequency Relaxation of Oil-Paper Insulation

The dielectric and impedance spectra of TlGaSe2 crystals have been studied at temperatures in the 100–500 K range in the alternating current (AC [Formula: see text]1 V). It has been shown that the conductivity of TlGaSe2 crystals is mainly an ionic characteristic at temperatures above 400 K. The well-defined peak at the frequency dependence of the imaginary part of impedance [Formula: see text] is observed in the 215–500 K temperature range. In a constant field, there occurs a significant decrease in electrical conductivity [Formula: see text] in due course. The ionic contribution to conductivity (76% at [Formula: see text]) has been estimated from a kinetic change in electrical conductivity [Formula: see text] under the influence of a constant electric field. The diagram analysis in a complex plane [Formula: see text] has been conducted by applying the method of an equivalent circuit of the substation. It has been determined that the average relaxation time of the electric module of the sample is [Formula: see text].

Download Full-text

Low-Frequency Relaxation Phenomena in α-LiIO3: The Nature and Role of Defects

Journal of Solid State Chemistry ◽

10.1006/jssc.2002.9683 ◽

2002 ◽

Vol 168 (1) ◽

pp. 76-84 ◽

Cited By ~ 10

Author(s):

Y. Mugnier ◽

C. Galez ◽

J.M. Crettez ◽

P. Bourson ◽

C. Opagiste ◽

...

Keyword(s):

Low Frequency ◽

Relaxation Phenomena ◽

Frequency Relaxation

Download Full-text

Dynamics of Ferroelectric and Nematic Liquid Crystals Confined in Porous Matrices

MRS Proceedings ◽

10.1557/proc-366-445 ◽

1994 ◽

Vol 366 ◽

Cited By ~ 1

Author(s):

Fouad M. Aliev

Keyword(s):

Liquid Crystals ◽

Heterogeneous Media ◽

Volume Fraction ◽

Low Frequency ◽

Pore Wall ◽

Polar Molecules ◽

Average Pore ◽

Surface Polarization ◽

The Difference ◽

Frequency Relaxation

ABSTRACTWe performed dielectric spectroscopy measurements to study dynamics of collective modes of ferroelectric (FLC) and molecular motion of nematic (NLC) liquid crystals with polar molecules confined in silica macroporous and microporous glasses with average pore sizes of 1000 Å (volume fraction of pores 40%) and 100 Å (27%) respectively. For FLC the Goldstone and the soft modes are found in macropores. The rotational viscosity associated with the soft mode is about 10 times higher in pores than in the bulk. These modes are not detected in micropores although low frequency relaxation is present. The last one probably is not connected with the nature of liquid crystal but is associated with surface polarization effects typical for two component heterogeneous media. The difference between the dynamics of orientational motion of the polar molecules of NLC in confined geometries and in the bulk is qualitatively determined by the total energy Fs of the interaction between molecules and the surface of the pore wall, which is found Fs ≈ 102erg/cm2.

Download Full-text