Achieving Ultralow Lattice Thermal Conductivity and High Thermoelectric Performance in SnTe by Alloying with MnSb2Se4

The manipulation of defect chemistry is crucial in the design of high-performance thermoelectric materials. Studies have demonstrated that alloying compounds within the I-V-VI2 family, such as AgSbTe2, NaSbTe2, etc., can effectively enhance the thermoelectric performance of SnTe by controlling the hole concentration and reducing the lattice thermal conductivity. In this paper, samples of SnTe alloyed with MnSb2Se4 were prepared, and the microstructure, electrical properties, and thermal properties were thoroughly investigated. Based on SEM and TEM analysis, it was observed that MnSb2Se4 can dissolve into SnTe during the preparation of the samples, which leads to the formation of various secondary phases with different compositions and point defects. Consequently, the lattice thermal conductivity is reduced to 0.44 W m-1 K-1 at 800 K, approaching the amorphous limit. Furthermore, the diffusion of the Mn and Sb elements leads to a significant improvement in the Seebeck coefficient through valence band convergence. The vacancy concentration in SnTe can also be modulated by alloying with MnSb2Se4. The findings indicated that MnSb2Se4 alloying can enhance the thermoelectric performance of SnTe through increasing the vacancy concentration, promoting valence band convergence, and introducing secondary phases. Consequently, a ZT value of 1.36 at 800 K for Sn1.03Te-5%MnSb2Se4 can be achieved.