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 Bi2S3, 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.