High ZT Value of Pure SnSe Polycrystalline Materials Prepared by High-Energy Ball Milling plus Hot Pressing Sintering

The research of thermoelectric materials is of great significance to solve the energy crisis and environmental problems. In this work, a series of pure SnSe bulk crystals were prepared by melting, high-energy ball milling, and hot pressing processes. The results show that the ZT value of the prepared pure SnSe polycrystalline material is up to 2.1 at 873 K. On the one hand, due to the reduction of grain size and lattice distortion caused by long-time high-energy ball milling, the lattice thermal conductivity is significantly reduced, which is only 0.18 W K–1 m–1 at 873 K. On the other hand, high-energy ball milling leads to the increase of Sn vacancies, which improves the conductivity of SnSe polycrystalline materials. Since the whole process of ball milling was carried out in a closed ball milling tank filled with high-purity argon, no oxidation of the SnSe powder is also a guarantee to obtain pure SnSe polycrystalline materials with high ZT value.