Strong texture in nanostructured bulk Bi_0.5Sb_1.5Te₃ leads to superior thermoelectric and mechanical performance

Bismuth telluride-based alloys are the most widely used thermoelectric (TE) materials. Despite this, zone-melted Bi₂Te₃-based alloys suffer from poor mechanical properties, and polycrystalline materials prepared by powder metallurgy often disrupt the desired texture due to their inherent anisotropic crystal structure. In this study, we achieved a synergistic integration of nanoscale structures, highly oriented texture, and intrinsic Bi_Te' antisite defects in P-type Bi_0.5Sb_1.5Te₃ bulk materials by employing layered directional sintering (LDS) on melt-spinning ribbons produced in a Bi-rich environment. The transmission electron microscopy analysis revealed regions of high-density distortions within the well-aligned nanograins, which play a crucial role in reducing lattice thermal conductivity. Ab initio simulations and Boltzmann transport equation analyses reveal that the Bi_Te' antisite defects generate both resonance states and additional phonon scattering channels. This full-spectrum phonon scattering coupled with high carrier mobility leads to a maximum figure of merit (ZT) of 1.54 at 375 K. Additionally, the compressive strength of the material reaches 140 MPa, which is 3.5 times higher than that of zone-melted counterparts. This work offers an efficient pathway for the facile preparation of high-performance Bi₂Te₃-based thermoelectric materials.