The Synthetic Search for Better Thermoelectrics

Abstract

Despite a recent push to find better bulk thermoelectric (TE) materials for use near room temperature and pressure, no material has yet been reported whose ZT is significantly improved over that of the Bi₂Te₃-Sb₂Te₃alloys (where ZT≅1). These same alloys have been used in commercial TE devices for more than 30 years. At first glance, this may seem surprising, since the microscopic theory of thermoelectric effects in semiconductors was essentially fully developed in the 1960s and has been nicely summarized in recent reviews.^1–5We know what properties we want, but we do not have any compounds that meet the many criteria for significant improvements in ZT. Yet TE research in the last half decade has refined the sense of what is needed, in terms of the composition and structure of materials classes that would have the characteristics necessary to make significant advances. In another approach, recent experiments by Badding et. al. on commercial Bi₂Te₃alloys show that increases in ZT by factors of 2 or more occur under non- hydrostatic pressure.⁶It seems possible that by suitable chemical modification of Bi₂Te₃, materials could be prepared that reach the same or higher ZT at atmospheric pressure.