Features Of Dielectric Relaxation Research Articles

Universal installation for studying structural defects in electrical and optical fiber materials

A universal device for experimentally studying the migration of microscopic structure defects and the features of dielectric relaxation is proposed. it allows using the thermo stimulated depolarization method, in combination with the measurement of the tangent of the angle of dielectric losses and the thermo stimulated polarization current, to perform dielectric spectroscopy of hydrogen-bonded crystals and perform analysis of the properties and parameters of structure defects. A smaller (in comparison with the existing installation) additional compact device for measuring small values of electrical capacitance and the tangent of the angle of dielectric losses, including an electrometer B7-30, was designed, measurement was carried out using a q-factor meter VM 560. When measuringtgδ > 0.1, the VM-507 device was used. An experimental methodology is proposed that allows, in combination with the method of minimizing the comparison function (MFC - method), with a high degree of accuracy, to calculate the molecular characteristics of structural defects in composite materials based on semiconductors and dielectrics used in the electrical and optical fiber industry, electric power and insulation technology.

Note: Effects of adding a viscosity-increasing 2 nm-size molecule on dielectric relaxation features and the dynamic heterogeneity view

To investigate the extent to which dynamic heterogeneity determines the relaxation features, we studied the effect of adding a viscosity-increasing, ∼2 nm size polyhederal oligomeric silsesquioxane (POSS) molecule on dielectric relaxation. Addition of POSS increased the relaxation time of the α-process, τ(m,α), and decreased the non-exponential response parameter, β, which is compatible with the dynamic heterogeneity view. But β varied monotonically with the composition, and there was little variation of β with the temperature, which seems incompatible with that view. Effects of adding nm-size particles in simulations may reveal how the size of dynamically heterogeneous regions affects τ(m,α) and β.

Dielectric relaxation in BiLi0.6W0.4O3 ceramics

The low-frequency process of dielectric relaxation in the new lead-free compound BiLi0.6W0.4O3 prepared by conventional ceramic technology is studied. The features of dielectric relaxation are discussed in terms of a model of interaction between the domain boundaries and point defects of a crystalline lattice.

Low temperature dielectric relaxation phenomena in relaxor ferroelectric strontium barium niobate single crystals

Abstract Low temperature (15∼300K) dielectric permittivities of tungsten bronze Sr1–xBaxNb2O6 (SBN(1–x)%, 1–x=0.50, 0.61, and 0.75) single crystals were studied using dielectric spectrum techniques. Two distinct dielectric relaxation features were observed in all three crystal compositions. The dielectric anomaly at temperature range ∼(150K–300K) is presumably associated with the incommensurate (ICS) superlattice transformation identified by high resolution TEM (Bursill and Lin)1 No experimental evidence of phase transition was found in the measurement regime for the dielectric anomaly observed at temperature below 150K. Dielectric properties of the poled crystals indicate that the ICS related dielectric anomaly is strongly dependent on the polarization-strain coupling along the c-direction, while the second low temperature relaxation is associated to the polarization fluctuation in the a-b plane related to the relaxor nature of the SBN solid solution system. The experimental results further substantiate ...

Relaxation process due to molecular inclusions in non-crystalline solids

The dielectric, thermodynamic and electric conduction behaviour of amorphous solids with three types of inclusions are described. In the first, or the self-inclusion in glasses, the features of dielectric relaxation due to localized rotational diffusion have a remarkable resemblance to those of the rotation of guest molecules in clathrate structures. But here, the availability of the various configurational states to molecules in the local regions makes a relatively greater contribution to the thermodynamic behaviour of a glass than is observed in clathrates. The number of such self-inclusions decreases as a glass spontaneously densifies on ageing. In this respect, the features attributable to such inclusions in a non-crystalline solid differ from those of a crystalline solid. In the second, - 20 A size inclusions or microdomains of strained a-AgI (bec lattice) are randomly distributed in AgI-AgP03 glasses. The electrical conductivity due to such inclusions follows a power law characteristic of site percolation with a percolation threshold of 0.3, critical exponent 3.3, vulnerability 4.8 and the number of contact sites 2.7. In the third, the part of the repeat unit of a randomly oriented poly(vinyl pyrrolidone) becomes incorporated as inclusions in the distorted, H-bonded, cage-like structures formed by the water molecules. The features of dielectric relaxation of water molecules in the solid aqueous solution of the polymer are similar to those of ice clathrates containing a guest molecule similar in size to pyrrolidone, but the respective temperature dependence of their rates differ.