High thermoelectric figure-of-merit in p-type nanostructured (Bi,Sb) ₂Te ₃ fabricated via hydrothermal synthesis and evacuated-and-encapsulated sintering

High ZT values of nanostructured Bi _2-xSb _xTe ₃ for energy conversion are fabricated by hydrothermal methods followed by cold-pressing and sintering in an evacuated and encapsulated ampoule. We show that the sample with a nominal composition of x = 1.55 exhibits a dimensionless figure of merit ZT = 1.65 at 290 K and 1.75 at 270 K with significant 60-70% improvement of that of the commercial state-of-the-art Bi ₂Te ₃ materials around room temperature. The significant ZT improvement arises from the much-reduced thermal conductivity. The low thermal conductivity is mainly due to the increased phonon scattering in the nanostructured materials.