Enhancing thermoelectric performance of SrFBiS2−xSex via band engineering and structural texturing

• Published in: Journal of Materiomics Vol. 8; no. 2; pp. 302 - 310
• Main Authors: Hai Huang, Chen Lin, Shijing Li, Kai Guo, Jianxin Zhang, Wanyu Lyu, Jiye Zhang, Juanjuan Xing, Ying Jiang, Jiong Yang, Jun Luo
• Format: Journal Article
• Language: English
• Published: Elsevier 01.03.2022
• Subjects: Carrier mobility; Energy band engineering; Layered compound; SrFBiS2; Texturing
• ISSN: 2352-8478
• DOI: 10.1016/j.jmat.2021.09.006

SrFBiS2 is a quaternary n-type semiconductor with rock-salt-type BiS2 and fluorite-type SrF layers alternately stacked along the c axis. The tunability of the crystal and electronic structures as well as the intrinsically low thermal conductivity make this compound a promising parent material for thermoelectric applications. In the current work, we show that alloying of Se and S in SrFBiS2 reduces the optical band gap with the second conduction band serving as an electron-transport medium, simultaneously increasing the electron concentration and effective mass. In addition, the raw material Bi2Se3 is shown to act as liquid adjuvant during the annealing process, favoring preferred-orientation grain growth and forming strengthen microstructural texturing in bulk samples after hot-pressed sintering. Highly ordered lamellar grains are stacked perpendicular to the pressure direction, leading to enhanced mobility along this direction. The synthetic effect results in a maximum power factor of 5.58 μW cm−1 K−2 at 523 K for SrFBiSSe and a peak zT = 0.34 at 773 K, enhancements of 180% compared with those of pristine SrFBiS2.