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New Scaling for AC Properties of Percolating Composite Materials

Published online by Cambridge University Press:  03 September 2012

F. Brouers  and
A.K. Sarychev
F. Brouers
Affiliation:
Etude Physique des Matériaux, Institut de Physique, University of Liège, 4000 Liège, Belgium
A.K. Sarychev
Affiliation:
Etude Physique des Matériaux, Institut de Physique, University of Liège, 4000 Liège, Belgium
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Abstract

In real conductor-insulator composites one observes a sharp change of the dc resistivity and a large increase of the low frequency dielectric constant at the percolation threshold Pc. However in many cases the a.c. data do not follow the scaling behaviour predicted by the percolation theory. To account for these discrepancies, we have proposed an alternative model which incorporates quantum tunnelling into the percolation theory. This models leads to a new “tunnelling” scaling law for the complex conductivity which gives rise for concentration below Pc to an exponential variation of the d.c. conductivity with concentration and a dispersion of the ac complex conductivity with non universal exponents. This new scaling law depends on two new exponents and reduces to the usual one for metal concentration well above Pc:. We apply this more general scaling to discuss the relation between the film morphology and the low frequency dispersion in granular metallic composites.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 367: Symposium P – Fractal Aspects of Materials , 1994 , 231
Copyright
Copyright © Materials Research Society 1995

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