Modulation of Vacancy Defects and Texture for High Performance n‐Type Bi2Te3 via High Energy Refinement

The carrier concentration in n‐type layered Bi2Te3‐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 Bi2Te2.7Se0.3 + 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 Bi2Te2.7Se0.3 + 0.05 wt.% SbI3 and commercial p‐type Bi0.5Sb1.5Te3 legs is fabricated, which generates the large maximum temperature difference (ΔTmax) 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 Bi2Te3, thereby promoting its applications in harsh conditions. Grain refinement strongly strengthens the non‐basal slip of Bi2Te3‐based thermoelectric material, and then increase the carrier concentration, hindering the practical preparation of n‐type Bi2Te3 by ball milling method. In this work, enhancing the ball milling energy can facilitate the recovery effect during hot pressing, which can reduce and stabilize the carrier concentration and achieve high thermoelectric and mechanical performances.