SCALING BEHAVIOR OF THE THERMOPOWER IN A 2-COMPONENT COMPOSITE NEAR A PERCOLATION-THRESHOLD

An exact relation between the bulk effective Seebeck coefficient alpha(e) of a composite conductor and the bulk effective electrical and thermal conductivities sigma(e) and gamma(e) is used to study the scaling behaviour of alpha(e) near percolation. The behaviour turns out to be quite rich, as a result of its dependence on three dimensionless small parameters, namely, the electrical and thermal conductivity ratios of the two components sigma(I)/sigma(M), gamma(I)/gamma(M), and the distance away from the percolation threshold DELTAp = p(M) - p(c). The behaviour of the thermoelectric figure of merit Z(e) in the different parts of the critical region is also discussed.