Enhanced the thermoelectric properties of n-type Bi2S3 polycrystalline by iodine doping

Bi2S3 is one of eco-friendly alternative compounds for thermoelectric devices. However, the low electrical conductivity of pristine Bi2S3 is the main restriction for a high ZT value. In this work, a series of iodine doped Bi2S3 polycrystalline samples are successfully prepared by melting combined with plasma activated sintering (PAS), and the relationships among composition, microstructure and thermoelectric properties are investigated. The X-ray diffraction (XRD) results shows that the content of the secondary phase BiS2 is closely related to the doped concentration of iodine. The doped concentration of iodine can directly affect the electrical conductivity and the Seebeck coefficient, resulting in the relatively high power factor of 3.1 μWcm−1K−2 at 773 K while doping 1.0 mol% BiI3. Moreover, the thermal conductivity is also reduced moderately. As a result, a maximum ZT value of 0.58 is obtained, which is 4 times higher than that of pristine Bi2S3.