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

Graphical abstract Highlights • SnSe crystal is grown by a novel Horizontal Bridgman method. • As-grown SnSe crystal is about 100 × 50 × 15 mm3 in dimensions. • SnSe crystal has higher electronic/thermoelectric transport properties than SnSe polycrystal. • The largest ZT crystal is 0.92 and maximum ZT polycrystal is 0.5 around 793 K. Abstract In this work, SnSe thermoelectric (TE) single crystals with size of 100 × 50 × 15 mm3 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 PF crystal along (100) facet was 5.08 μWcm−1 K−2 and the maximum PF polycrystal 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 (k tot-polycrystal) was always lower than that of single-crystal SnSe (k tot-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. [ABSTRACT FROM AUTHOR]