Carrier and microstructure tuning for improving the thermoelectric properties of Ag8SnSe6 via introducing SnBr2
Zhonghai Yu, Xiuxia Wang, Chengyan Liu, Yiran Cheng, Zhongwei Zhang, Ruifan Si, Xiaobo Bai, Xiaokai Hu, Jie Gao, Ying Peng, Lei Miao
Abstract
Abstract The argyrodite compounds (A (12− n ) m/m+ B n + X 6 2− (A m + = Li + , Cu + , and Ag+; B n + = Ga 3+ , Si 4+ , Ge 4+ , Sn 4+ , P 5+ , and As 5+ ; and X 2− = S 2− , Se 2− , or Te 2− )) have attracted great attention as excellent thermoelectric (TE) materials due to their extremely low lattice thermal conductivity Among them, Ag 8 SnSe 6 -based TE materials have high potential for TE applications. However, the pristine Ag 8 SnSe 6 materials have low carrier concentration (< 10 17 cm −3 ), resulting in low power factors. In this study, a hydrothermal method was used to synthesize Ag 8 SnSe 6 with high purity, and the introduction of SnBr 2 into the pristine Ag 8 SnSe 6 powders has been used to simultaneously increase the power factor and decrease the thermal conductivity ( κ ). On the one hand, a portion of the Br − ions acted as electrons to increase the carrier concentration, increasing the power factor to a value of ∼698 µW·m −1 ·K −2 at 736 K. On the other hand, some of the dislocations and nanoprecipitates (SnBr 2 ) were generated, resulting in a decrease of κ 1 (−0.13 W·m −1 ·K −1 ) at 578 K. As a result, the zT value reaches ∼1.42 at 735 K for the sample Ag 8 Sn 1.03 Se 5.94 Br 0.06 , nearly 30% enhancement in contrast with that of the pristine sample (−1.09). The strategy of synergistic manipulation of carrier concentration and microstructure by introducing halogen compounds could be applied to the argyrodite compounds to improve the TE properties.