Enhancement of the Thermoelectric Performance of 2D SnSe Nanoplates through Incorporation of Magnetic Nanoprecipitates

Single crystals of tin selenide (SnSe), a layered material, have recently drawn massive attention in the field of thermoelectrics for its low thermal conductivity and high thermoelectric figure of merit (zT). However, nanocrystalline SnSe always remains a better choice for thermoelectric applications owing to its simple synthesis and machinability. On the other hand, enhancement of the thermoelectric performance can be achieved by the incorporation of magnetic nanoprecipitates in a thermoelectric host matrix. Herein, we have demonstrated the significant enhancement in the thermoelectric performance of the two-dimensional (2D) nanoplates of SnSe by introducing magnetic Gd dopants, which are synthesized and scaled up (∼10 g) by a low-temperature hydrothermal method. The p-type carrier concentration increases significantly upon 3 mol % Gd addition in SnSe nanoplates due to phase separation of Gd2Se3 nanoprecipitates (2–5 nm) and subsequent Sn2+ vacancy formation. Thus, the thermoelectric power factor has been markedly enhanced to 6.7 μW/(cm K2) at 868 K compared to that of the pristine SnSe nanoplates. The presence of magnetic fluctuations induced by small nanoprecipitates of Gd2Se3 provides additional scattering of the phonons in SnSe, which reduces the lattice thermal conductivity significantly to 0.41 W/(m K) at 868 K in Sn0.97Gd0.03Se. We have achieved a zT of ∼1 at 868 K for the spark plasma sintered (SPS) Sn0.97Gd0.03Se nanoplates along the perpendicular to the pressing direction.