THERMOELECTRIC PROPERTIES OF A COMPOSITE MEDIUM

We study the thermoelectric properties of a composite medium. Various approximations are developed for calculating the matrix Q(e) of the bulk effective transport coefficients of the medium, including exact upper and lower bounds for Q(e) under various conditions. Results are especially detailed for two-component composites, where a field decoupling transformation is used to reduce the thermoelectric problem to two uncoupled quasi-conductivity problems. Exact bounds are then obtained for the absolute thermopower alpha-e and the thermoelectric figure of merit Z(e) in two-component composites. We prove that Z(e) of the composite can never exceed the largest value of Z in any component. Some of these results are extended to certain classes of multicomponent composites.