Heavy Rare Earth Element Gd Enhancing Thermoelectric Performance in p-Type Polycrystalline SnSe via Optimizing Carrier Transport and Density of States

Tin selenide(SnSe) material exhibits very excellent thermoelectric properties in both p- and n-type single crystals, benefiting from advantageous electronic structure and ultra-low lattice thermal conductivity. However, poor mechanical properties and time-consuming production limit its practical application, and polycrystalline SnSe has attracted great attention in recent years. Herein, the SnSe microplates are prepared by a facile solvothermal method and compacted by spark plasma sintering (SPS). With enhanced electrical conductivity( σ ) and optimized Seebeck coefficient( S ) benefited from the Sn vacancies and increased density of states effective mass by the incorporating of heavy rare earth element Gd, an enhanced power factor(PF) value of about 0.86 mW/(m·K 2 ) is realized in the p-type polycrystalline Sn 0.985 Gd 0.015 Se sample. Combined with the medium total thermal conductivity k tot and lattice thermal conductivity k lat of 0.7 and 0.56 W/(m·K), respectively, an enhanced peak dimensionless figure of merit( ZT ) of ca. 1.1 was achieved at 873 K along vertical to the SPS pressing direction. The average ZT was also improved as compared to that of the pristine SnSe sample.