Synergistic Effect of Bismuth and Indium Codoping for High Thermoelectric Performance of Melt Spinning SnTe Alloys.

In this work, a nonequilibrium melt spinning (MS) technology combined with hot pressing was adopted for rapid synthesizing of SnTe compounds in less than 1 h. The refined microstructure generated by MS significantly decreases the lattice thermal conductivity. Compared to the pristine SnTe sample prepared by traditional melting and long-term annealing, the melt-spun one reveals a 15% lower thermal conductivity of ∼6.8 W/m K at room temperature and a 10% higher zT of ∼0.65 at 900 K. To further improve the electrical transport properties of the SnTe system, elements of Bi and In are introduced. It was found that Bi and In codoping can enhance Seebeck coefficients in a broad temperature range via optimizing carrier density and introducing resonant states. Point defects and nanoparticles introduced by Bi and In codoping remarkably enhanced phonon scattering and decreased lattice thermal conductivities. Finally, a significant enhancement on the thermoelectric performance was achieved: a peak zT of 1.26 at 900 K and an average zT of ∼0.48 over the temperature range of 300-900 K are obtained in Sn0.9675Bi0.03In0.0025Te. This work demonstrates that MS combined with appropriate doping could be an effective strategy to improve the thermoelectric performance of SnTe-related samples.