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 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 Bi2Te2.7Se0.3 alloys only 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 averaged ZT of 0.88 within 300-500 K in the 0.5% MgB2-doped Bi2Te2.7Se0.3 (BTSMB) alloys. The peak ZT and average ZT of our optimized BTSMB samples are comparable and higher than that of state-of-the-art commercial ZM ingot respectively. Moreover, the optimized BTSMB sample also exhibits almost 70% enhancement in hardness compared with the ZM ingot. Our results demonstrate the great potential of MgB2 doping strategy for mass production of SPS-derived Bi2Te3-based alloys in one-step sintering.