High-Thermoelectric Performance of Nanostructured Bismuth Antimony Telluride Bulk Alloys

TLDR

The dimensionless thermoelectric figure of merit (ZT) in bismuth antimony telluride bulk alloys has remained around 1 for more than 50 years. The authors fabricated nanocrystalline BiSbTe bulk alloys by hot‑pressing ball‑milled nanopowders from crystalline ingots under inert conditions, and demonstrated cooling devices achieving temperature differences up to 119 °C at hot‑side temperatures up to 150 °C. The nanocrystalline alloys reach a peak ZT of 1.4 at 100 °C (≈ 1.2 at room temperature and 0.8 at 250 °C), attributed to reduced thermal conductivity from enhanced phonon scattering at grain boundaries and defects, making them suitable for both cooling and power generation and paving the way for low‑cost high‑performance bulk thermoelectrics.

Abstract

The dimensionless thermoelectric figure of merit (ZT) in bismuth antimony telluride (BiSbTe) bulk alloys has remained around 1 for more than 50 years. We show that a peak ZT of 1.4 at 100 degrees C can be achieved in a p-type nanocrystalline BiSbTe bulk alloy. These nanocrystalline bulk materials were made by hot pressing nanopowders that were ball-milled from crystalline ingots under inert conditions. Electrical transport measurements, coupled with microstructure studies and modeling, show that the ZT improvement is the result of low thermal conductivity caused by the increased phonon scattering by grain boundaries and defects. More importantly, ZT is about 1.2 at room temperature and 0.8 at 250 degrees C, which makes these materials useful for cooling and power generation. Cooling devices that use these materials have produced high-temperature differences of 86 degrees , 106 degrees , and 119 degrees C with hot-side temperatures set at 50 degrees, 100 degrees, and 150 degrees C, respectively. This discovery sets the stage for use of a new nanocomposite approach in developing high-performance low-cost bulk thermoelectric materials.