Growth of large size SnSe single crystal and comparison of its thermoelectric property with polycrystal

Abstract In this work, SnSe thermoelectric (TE) single crystals with size of 100 × 50 × 15 mm 3 was grown by a Horizontal Bridgman method. The as-grown crystals had standard Pnma space group at room temperature and its measured stoichiometric ratio (Sn:Se) was nearly 1:1. Besides, polycrystalline SnSe was also prepared by a hot-pressing technique for comparison. The largest power factor PFcrystal along (100) facet was 5.08 μWcm−1 K−2 and the maximum PFpolycrystal perpendicular to pressure direction was only 2.01 μWcm−1 K−2, which means the grain orientation has significant influence on the electrical properties of SnSe. The measured total thermal conductivity of polycrystalline SnSe (ktot-polycrystal) was always lower than that of single-crystal SnSe (ktot-crystal) during the whole temperature range except near the phase-transition temperature, and their smallest values were all reached 0.44 Wm−1 K−1. Finally, single-crystal SnSe shows a peak ZT of 0.92, which is much excellent than that of polycrystalline SnSe (ZT = 0.5) around 793 K.