Nanostructured n-Type Polycrystalline SnSe Materials for Thermoelectric Applications

SnSe with intrinsically low lattice thermal conductivity is considered to be one of the most promising thermoelectric materials. However, the low electrical conductivity limits its further application. To improve the electrical conductivity, the metallic chlorides and metallic elements are co-doped in the SnSe matrix. Herein, nanostructured polycrystalline Sn 1– y Bi y Se 0.95 + x wt % NdCl 3 ( x = 0, 0.25, 0.5, 0.75; y = 0.005, 0.01, 0.015) samples are prepared by the melting method and spark plasma sintering (SPS). A σ of ∼37.8 S cm –1 and PF of ∼651 μW m –1 K –2 are obtained at 773 K for the 0.5 wt % NdCl 3 sample, owing to the release of a lot of electrons by the introduction of NdCl 3 .In addition, with heavy-element Bi doping, the lattice thermal conductivity is further suppressed. A κ l of ∼0.37 W m –1 K –1 is achieved at 773 K for the Bi 0.01 sample, owing to the mass fluctuation, point defects, and multiscale secondary precipitates, such as Nd 5 Sn 3, Bi 4 Se 3, Nd, SnNd x Cl y, and SnBi. Consequently, a peak ZT value of ∼1.07 at 773 K and a ZT ave value of 0.73 from 573 to 773 K are obtained for the Sn 0.99 Bi 0.01 Se 0.95 + 0.5 wt % NdCl 3 sample, which is competitive with potential for application compared with other works of n-type polycrystalline SnSe materials. It has a great application prospect to use waste heat to generate electricity in the medium-temperature region.