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New Scaling for AC Properties of Percolating Composite Materials
Published online by Cambridge University Press: 03 September 2012
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.
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- Copyright © Materials Research Society 1995