Highly Enhanced Thermoelectric Properties of Bi/Bi₂S₃ Nanocomposites

Bismuth sulfide (Bi₂S₃) has been of high interest for thermoelectric applications due to the high abundance of sulfur on Earth. However, the low electrical conductivity of pristine Bi₂S₃ results in a low figure of merit (ZT). In this work, Bi₂S₃@Bi core-shell nanowires with different Bi shell thicknesses were prepared by a hydrothermal method. The core-shell nanowires were densified to Bi/Bi₂S₃ nanocomposite by spark plasma sintering (SPS), and the structure of the nanowire was maintained as the nanocomposite due to rapid SPS processing and low sintering temperature. The thermoelectric properties of bulk samples were investigated. The electrical conductivity of a bulk sample after sintering at 673 K for 5 min using Bi₂S₃@Bi nanowire powders prepared by treating Bi₂S₃ nanowires in a hydrazine solution for 3 h is 3 orders of magnitude greater than that of a pristine Bi₂S₃ sample. The nanocomposite possessed the highest ZT value of 0.36 at 623 K. This represents a new strategy for densifying core-shell powders to enhance their thermoelectric properties.