Thermoelectric Properties of Nanocrystalline Bi2(Te1−xSex)3 Prepared by High-Pressure Sintering

Bi2(Te1−xSex)3 (x = 0, 0.03, 0.05, 0.07, 0.10) bulk materials were prepared by high-pressure (6.0 GPa) sintering (HPS) at 673 K. The samples were then annealed under vacuum, at 633 K, for 36 h. Phase composition, morphology, and thermoelectric (TE) properties were characterized. The alloys consisted of nanoparticles before and after annealing. Such nanostructures effectively reduce lattice thermal conductivity by enhancing phonon scattering. Substitution of tellurium by selenium had a substantial effect on the electron transport properties of the Bi2(Te1−xSex)3 alloys. HPS with annealing can improve TE properties by improving the electron transport properties and simultaneously reducing the lattice thermal conductivity of nanostructured samples. A peak thermoelectric figure of merit (ZT) of 0.81 at 373 K was achieved for the annealed sample with x = 0.10; this value ZT was approximately 8% higher than that of n-type zone-melted material, making these materials more attractive for commercial applications.