SrFBiS_(2) is a quaternary n-type semiconductor with rock-salt-type BiS_(2) and fluorite-type SrF layers alternately stacked along the c axis.The tunability of the crystal and electronic structures as well as the intr...SrFBiS_(2) is a quaternary n-type semiconductor with rock-salt-type BiS_(2) 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 thermo-electric applications.In the current work,we show that alloying of Se and S in SrFBi_(S) 2 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 Bi_(2)Se_(3) 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 μm W 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 SrFBiS_(2).展开更多
基金This work was financially supported by the National Key Research and Development Program of China(2018YFA0702100)the National Natural Science Foundation of China(21771123,52072234)J.Zhang is grateful for the support by the Open Project of Jiangsu Key Laboratory for Carbon-Based Functional Materials&Devices(KJS2023).
文摘SrFBiS_(2) is a quaternary n-type semiconductor with rock-salt-type BiS_(2) 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 thermo-electric applications.In the current work,we show that alloying of Se and S in SrFBi_(S) 2 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 Bi_(2)Se_(3) 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 μm W 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 SrFBiS_(2).
