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–VI 2 family, such as AgSbTe 2, NaSbTe 2, 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 MnSb 2 Se 4 were prepared, and the microstructure, electrical properties, and thermal properties were thoroughly investigated. Based on SEM and TEM analysis, it was observed that MnSb 2 Se 4 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 MnSb 2 Se 4 . The findings indicated that MnSb 2 Se 4 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 Sn 1.03 Te-5%MnSb 2 Se 4 can be achieved.