Simultaneous Optimization of Electrical and Thermal Transport Properties of BiSbSe1.50Te1.50 Thermoelectrics by Hot Deformation

As a typical multi-layered compound thermoelectric (TE) material, BiSbSe1.50Te1.50, can be utilized to fabricate p-n junctions with the same chemical composition. It has great potential in the development and design of high-performance TE devices due to its ability to avoid lattice mismatch incompatibility and harmful band misalignment. However, the TE performance of n-type BiSbSe1.50Te1.50 is limited due to poor electrical transport properties, which hinders its further application in TE devices. Therefore, it is of great significance to improve the TE performance by enhancing the electrical transport properties while maintaining low thermal conductivity. In this work, a series of n-type BiSbSe1.50Te1.50 hot deformation samples were prepared by solid-state reaction combined with hot pressed sintering. It is found that the preferred orientation and nanoscale lamellar structures with large surface areas form in hot-deformed samples. The donor-like effect elevates the carrier concentration, while these lamellar structures facilitate higher carrier mobility by providing expressways for carriers, giving rise to the enhanced electrical conductivity. Additionally, various and abundant multiscale defects are introduced into samples, evoking strong phonon scattering with different frequencies and thus lowering the thermal conductivity. The electrical and thermal transport properties have been synergistically optimized by hot deformation, realizing the improvement of TE properties for n-type BiSbSe1.50Te1.50. As a result, a peak thermoelectric figure of merit (ZT) of 0.50 at 500 K is achieved for the hot-deformed sample, which increased similar to 138% compared to the undeformed sample (0.21). This work establishes a foundation for further advancement of the preparation for BiSbSe1.50Te1.50 TE devices with high conversion efficiency and homogeneous structure.