Broadband ac conductivity of conductor-polymer composites

Abstract

Type of publicationArticle (peer-reviewed) The electrical conductivity of a composite model system formed by highly structured carbon black ͑CB͒ filled, within an amorphous polymer, poly͑ethylene terephtalate͒ composite is studied. The dc conductivity as a function of CB content follows a scaling law of the type ϰ(pϪp c ) t yielding for the percolation concentration, p c ϭ0.011 and for the exponent, tϭ2.17. The analysis of the temperature dependence of the conductivity suggests that for temperatures larger than 45 K, conduction can be ascribed to thermal fluctuation induced tunneling of the charge carriers through the insulating layer of polymer separating two CB aggregates. At lower temperatures, conductivity becomes temperature independent, which is typical of conventional tunneling. The frequency dependence of the conductivity is also studied between dc and 10 9 Hz. By the introduction of a shift factor a p , a procedure for the construction of a master curve based on a ''time-length equivalence principle'' is proposed. Finally, a model is introduced to describe the frequency dependence of the conductivity of CB-filled composites based on the behavior of charge carriers placed in a fractal object.

A review and analysis of electrical percolation in carbon nanotube polymer composites

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Universality of ac conduction for generalized space-charge transport in ordered solids

“…Nevertheless, this merely shifts the argument of striking generality as either of these critical limits thus always seems to be achieved experimentally, despite the wide range of sample parameters for which the universality is observed. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Although the implications of space charge are commonly included in the interpretation of I − V characteristics on insulating materials, this seems not to be the case in the field of ac conduction and only a few papers have pointed in this direction. 3,17 In this paper, we will demonstrate that the use of the drift-diffusion equations in combination with a realistic model for the ohmic contact is in fact sufficient to obtain an ac conductivity that follows ͑͒ϳ s with 0 Ͻ s ഛ 1 and that obeys Taylor-Isard scaling.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] The frequency dependent conductivity is characterized by an approximate power law behavior ͑͒ ϰ s in which s is observed to be 0 Ͻ s ഛ 1. By rescaling the frequency dependent conductivity at various temperatures following Taylor-Isard scaling, master curves can be created that appear to be independent of the actual disordered material.…”

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