Bi(2-x)SbxTe3 Thermoelectric Composites with High Average zT Values: From Materials to Devices

(Bi,Sb)Te-based materials have drawn extensive attention for nearly two centuries as one of the most successful commercial thermoelectric (TE) materials. However, Bi(2-x)SbxTe3 composites with remarkable average figure of merit (zTavg) values are highly desired in terms of the great contribution on expanding the applying temperature ranges of the commercial devices. Herein, Bi0.35Sb1.65Te3 compound with outstanding zTavg value of about 1.18 (integrate from 298 to 498 K) was obtained via delaying the bipolar effect by precipitating multi-scale Sb2Te3 inclusions. The power factor (PF) was enhanced from 2.1×10−3 Wm−1 K−2 (Bi0.5Sb1.5Te3) to 4.3×10−3 Wm−1 K−2 (Bi0.35Sb1.65Te3) by optimizing the carrier concentration from 1.9×1019 cm−3 to 3.9×1019 cm−3 via adjusting the proportions of Bi:Sb. Correspondingly, the lattice thermal conductivities (kl) were distinctly suppressed by the additional multiple phonon scattering resulting from the Sb2Te3 precipitates. Consequently, a remarkable zTmax, as high as ~1.35 at 373 K was obtained in the Bi0.35Sb1.65Te3 sample. The temperature difference ( T, 6.0 A current) of the TE device that assembled with the commercial N-type Bi(Te,Se) ingot has reached up to 66.9 K. The high zTavg, zTmax and T values will further promote the commercial applications of (Bi,Sb)Te-based materials in a wide temperature range.