Enhanced thermoelectric performance with improved mechanical strength in Bi₂S₃/graphite composites

In spite of possessing high Seebeck coefficient and low thermal conductivity, Bi₂S₃ suffers from poor electrical conductivity, which makes it challenging to use for application in thermoelectric power generator (TEG). In the present work, we have used graphite (G) to improve the electron transport in Bi₂S₃ by making a composite. Here, we have obtained ZT∼0.15 at room temperature in n-type Bi₂S_3, which is much higher than that reported for sulphides at room temperature. The inclusion of graphite in Bi₂S₃, provides a conductive pathway for the easy transport of electrons, and leads to a surge in electrical conductivity. As a result, a high thermoelectric power factor ∼643 μW/m-K² is attained, which is 30 times higher than that of pristine Bi₂S₃ at room temperature. The maximum ZT ∼0.3 is obtained for 1.5 wt% graphite-Bi₂S₃ composite at 705 K temperature. Furthermore, the mechanical strength of Bi₂S₃ is found to be significantly improved by graphite inclusion, which offers better load bearing capacity for practical application as TEG.