Record Seebeck coefficient and extremely low thermal conductivity in nanostructured SnSe

SnSe has been prepared by arc-melting, as mechanically robust pellets, consisting of highly oriented polycrystals. This material has been characterized by neutron powder diffraction (NPD), scanning electron microscopy, and transport measurements. A microscopic analysis from NPD data demonstrates a quite perfect stoichiometry SnSe_0.98(2) and a fair amount of anharmonicity of the chemical bonds. The Seebeck coefficient reaches a record maximum value of 668 μV K⁻¹ at 380 K; simultaneously, this highly oriented sample exhibits an extremely low thermal conductivity lower than 0.1 W m⁻¹ K⁻¹ around room temperature, which are two of the main ingredients of good thermoelectric materials. These excellent features exceed the reported values for this semiconducting compound in single crystalline form in the moderate-temperatures region and highlight its possibilities as a potential thermoelectric material