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 Bi_0.48Sb_1.52Te₃ 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, κ_lat is mostly diminished by the introduced phonon scattering centers comprising point defects, dislocations, and grain boundaries. Consequently, we achieved a ZT_max of 1.25 at 350 K and its average ZT_ave of 1.1 from 300 to 500 K in the (Bi_0.48Sb_1.52Te₃ + 3 wt % Te) + 0.12 wt % AgCuTe sample. Composed of this sample and commercial Bi₂Te_2.5Se_0.5, the fabricated TE module manifests a maximum power output density of 0.31 W cm^-2 (T_cold = 300 K and T_hot = 500 K). This work suggests that AgCuTe-doped Bi_0.48Sb_1.52Te₃ is promising for recovering low-grade thermal energy near room temperature.