Modulation of Vacancy Defects and Texture for High Performance n-Type Bi₂ Te₃ via High Energy Refinement

The carrier concentration in n-type layered Bi₂ Te₃ -based thermoelectric (TE) material is significantly impacted by the donor-like effect, which would be further intensified by the nonbasal slip during grain refinement of crushing, milling, and deformation, inducing a big challenge to improve its TE performance and mechanical property simultaneously. In this work, high-energy refinement and hot-pressing are used to stabilize the carrier concentration due to the facilitated recovery of cation and anion vacancies. Based on this, combined with SbI₃ doping and hot deformation, the optimized carrier concentration and high texture degree are simultaneously realized. As a result, a peak figure of merit (zT) of 1.14 at 323 K for Bi₂ Te_2.7 Se_0.3  + 0.05 wt.% SbI₃ sample with the high bending strength of 100 Mpa is obtained. Furthermore, a 31-couple thermoelectric cooling device consisted of n-type Bi₂ Te_2.7 Se_0.3  + 0.05 wt.% SbI₃ and commercial p-type Bi_0.5 Sb_1.5 Te₃ legs is fabricated, which generates the large maximum temperature difference (ΔT_max ) of 85 K at a hot-side temperature of 343 K. Thus, the discovery of recovery effect in high energy refinement and hot-pressing has significant implications for improving TE performance and mechanical strength of n-type Bi₂ Te₃ , thereby promoting its applications in harsh conditions.