Effect of Fast Hot Press Sintering on the Thermoelectric Properties of Polycrystalline Bi_0.85Sb_0.15 Alloys

Abstract Polycrystalline Bi1-xSbx alloys are leading candidates for low-temperature thermoelectric applications, yet the challenges remain in optimizing performance and mechanical properties. Here we combine the melt-quenching, long-term annealing and two-stage fast hot press (FHP) to fabricate fully dense polycrystalline Bi 0.85 Sb 0.15 . The microstructure and elemental distribution were examined, and the thermoelectric transport properties were measured. Compared with the once-sintered state, all re-sintered specimens show an increased Seebeck coefficient. Specifically, re-sintering at 503 K elevated the peak Seebeck coefficient ∣S∣ to 159 μV/K near 80 K and produced a higher power factor, although the additional porosity introduced in this step lowered the electrical conductivity. The results of Hall measurements show that the sample exhibited a carrier mobility on the order of 10 4 cm 2 V ‐1 s ‐1 and a carrier concentration on the order of 10 18 -10 19 cm ‐3 . Under a transverse magnetic field up to 1.5 T, ∣S∣ was further enhanced, κ was suppressed via magnetoresistance, and the peak ZT reached 0.63 at 300 K, Which is a 40% improvement over the zero field value obtained in the same polycrystalline. The results show that the microstructural tuning by staged FHP, combined with a moderate magnetic field, can enhance the thermoelectric properties of polycrystalline Bi0.85Sb0.15 alloys while maintaining mechanical robustness.