Optimized Thermoelectric Properties of Bi_0.48Sb_1.52Te₃ through AgCuTe Doping for Low-Grade Heat Harvesting

Zone-melted Bi2Te3-based alloys are the only commercially available thermoelectric (TE) materials, but they suffer from mediocre figure of merit (ZT) values and brittleness. In this work, we prepared Bi0.48Sb1.52Te3 sintered samples using a hot-pressing method and added tiny AgCuTe to improve the comprehensive properties. Because the carrier concentration is boosted by the AgCuTe addition, the bipolar effect at higher temperature is explicitly suppressed and the power factor is also improved in a broad temperature scope. Simultaneously, κlat is mostly diminished by the introduced phonon scattering centers comprising point defects, dislocations, and grain boundaries. Consequently, we achieved a ZTmax of 1.25 at 350 K and its average ZTave of 1.1 from 300 to 500 K in the (Bi0.48Sb1.52Te3 + 3 wt % Te) + 0.12 wt % AgCuTe sample. Composed of this sample and commercial Bi2Te2.5Se0.5, the fabricated TE module manifests a maximum power output density of 0.31 W cm–2 (Tcold = 300 K and Thot = 500 K). This work suggests that AgCuTe-doped Bi0.48Sb1.52Te3 is promising for recovering low-grade thermal energy near room temperature.