Enhanced Thermoelectric Performance of Te-Doped Bi2Se3-xTex Bulks by Self-Propagating High-Temperature Synthesis

Polycrystalline Bi2Se3-xTex (x = 0 similar to 1.5) samples were prepared by self-propagating high-temperature synthesis (SHS) combined with spark plasma sintering (SPS) and their thermoelectric properties were investigated. The SHS-SPS process can shorten the time with few energy consumptions, and obtain almost pure Bi2Se3-based phases. Consequently, the Se vacancies and anti-site defects contribute to the converged carrier concentration of similar to 2 x 10(19) cm(-3) while the increased carrier effective mass enhances the Seebeck coefficient to more than -158 V K-1 over the entire temperature range. The lattice thermal conductivity is suppressed from 1.07 Wm(-1) K-1 for the pristine specimen to similar to 0.6 Wm(-1) K-1 for Te-substitution samples at 300 K because of point defects caused by the difference of mass and size between Te and Se atoms. Coupled with the enhanced power factor and reduced lattice thermal conductivity, a high ZT of 0.67 can be obtained at 473 K for the Bi2Se1.5Te1.5 sample. Our results reveal that Te-substitution based on the SHS-SPS method is highly-efficient and can improve the thermoelectric properties of Bi2Se3-based materials largely.