Enhancement of thermoelectric power factor in composite thermoelectrics

The analytical properties of macroscopic transport coefficients of two-component composites are first used to discuss the thermoelectric power factor of such a composite. It is found that the macroscopic power factor can sometimes be greater than the power factors of both of the pure components, with the greatest enhancement always achieved in a parallel slabs microstructure with definite volume fractions for the two components. Some interesting examples of actual mixtures are then considered, where the components are a "high quality thermoelectric'' and a "benign metal,'' leading to the conclusion that considerable enhancement of the power factor is often possible, with but a modest reduction in the thermoelectric figure of merit, compared to those of the high quality thermoelectric component. Two possibilities for fabricating real composites with such improved thermoelectric properties emerge from this study: a parallel slabs microstructure of benign metal and high quality thermoelectric, and a sintered collection of benign metal grains, each of them coated by a thin shell of high quality thermoelectric. (C) 1999 American Institute of Physics. [S0021-8979(99)02112-X].