Improved Thermoelectric Properties of n-type Bi2S3 via anionic doping

Reference Presenter Authors
06-034 Guanjun QIAO Liu, G.(Jiangsu University); QIAO, G.(Jiangsu University); Yang, J.(Jiangsu University); Yan, J.(Jiangsu University); In order to improve the thermoelectric properties of n-type Bi2S3 matrials, a certain amount of BiI3 were added into Bi2S3 by a conventional melting method combined with plasma activated sintering (PAS). The XRD results shows that the content of the secondary phase BiS2 is observed. 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 ?Wcm-1K-2 at 773 K for the Bi2S3-1%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. Based on 1% iodine doping, a series of AgxBi2S3-1%BiI3 samples (x=0?0.02) were successfully prepared. The XRD results show that all the diffraction peaks are perfectly matched to the orthorhombic Bi2S3 without any detectable second phases. The synergistic effect of iodine and silver plays an important role in enhancing the electrical conductivity, but maintaining a high Seebeck coefficient simultaneously, resulting in a peak power factor of 3.95 ?Wcm-1K-2 at 723 K for the Ag0.0075Bi2S3 sample. Combined with a low thermal conductivity of 0.47 Wm-1K-1, the ZT value of 0.62 at 723 K is achieved for the Ag0.0075Bi2S3 sample. Furthermore, the effect of SbCl3 doping on the thermoelectric properties of Bi2S3 polycrystalline samples was investigated. With increasing doping concentration, the Bi2S3-based materials gradually evolves from the layered to the particle-like structures. The phonon scattering is enhanced by the increased grain boundaries and in situ nanoprecipitates, resulting in a low lattice thermal conductivity of ~0.36 Wm?1K?1 at 773 K for the Bi2S3-1%SbCl3 sample. The synergistic effect of antimony and chlorine substitutions can not only contribute to reduce the thermal conductivity but also to tune the electrical transport properties, which leads to a peak ZT value of ~0.65 at 773 K.
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