Electronic and Thermal Transport Properties of Nanostructured Thermoelectric Materials Sintered from Chemically Synthesized Tin Sulfide Nanoparticles and Effects of Ag and Se Doping

To shine light on the mechanisms involved in the doping of the sustainable thermoelectric material SnS with Ag and Se, we present a detailed investigation into Ag- and Se-doped SnS nanoparticles (NPs). SnS NPs, Ag-doped SnS NPs, and Ag-doped SnS1-xSex NPs were chemically synthesized and sintered into pellets by hot-press. The structure and thermoelectric, electronic, and thermal transport properties were then investigated using a variety of techniques. As a result, it was found that when Ag-doped SnS NPs were sintered two types of Ag were present in the sintered pellets: one in the form of segregated Ag-rich nanoprecipitates and the other in the form of interlayer intercalated Ag ions. In contrast, when Ag-doped SnS1-xSex NPs were sintered, Se was found to form a homogeneous solid solution. The effects of these three impurity-derived structures on the electronic and thermal transport properties were investigated. The final ZT values for SnS doped with 1.5 at% Ag (SnS:Ag) and SnS0.9Se0.1:Ag, in which SnS:Ag was further doped with Se, were 0.09 at 666 K and 0.14 at 667 K, respectively.