Simultaneous Enhancement of the Thermoelectric and Mechanical Performance in One-Step Sintered n-Type Bi₂Te₃-Based Alloys via a Facile MgB₂ Doping Strategy

The Bi₂Te₃-based alloys have been commercialized for the applications of energy harvesting and refrigeration for decades. However, the commercial Bi₂Te₃-based alloys produced by the zone-melting (ZM) method usually show poor mechanical strength and crack problems as well as the sluggish figure of merit ZT, especially for the less-progressed n-type samples. In this work, we have simultaneously enhanced the thermoelectric and mechanical performance of the one-step spark plasma sintering (SPS)-derived n-type Bi₂Te_2.7Se_0.3 alloys just by doping a small amount of superconducting material MgB₂ where Mg and B atoms can play significant roles in carrier density optimization and hardness enhancement. Besides the optimization of carrier density, the MgB₂ doping can also increase the carrier mobility but decrease the lattice and bipolar thermal conductivity, leading to a peak ZT of 0.96 at 325 K and an average ZT of 0.88 within 300-500 K in the 0.5% MgB₂-doped Bi₂Te_2.7Se_0.3 (BTSMB) alloys. The peak ZT and average ZT of our optimized BTSMB samples are comparable and higher than those of the state-of-the-art commercial ZM ingot. Moreover, the optimized BTSMB sample also exhibits almost 70% enhancement in hardness compared with the ZM ingot. Our results demonstrate the great potential of the MgB₂ doping strategy for mass production of SPS-derived Bi₂Te₃-based alloys in one-step sintering.