Scaling behaviour of the thermopower in a two-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 Delta p identical to 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.