Evolution of the Intrinsic Point Defects in Bismuth Telluride-Based Thermoelectric Materials.

In polycrystalline bismuth telluride-based thermoelectric materials, mechanical-deformation-induced donor-like effects can introduce a high concentration of electrons to change the thermoelectric properties through the evolution of intrinsic point defects. However, the evolution law of these point defects during sample preparation remains elusive. Herein, we systematically investigate the evolution of intrinsic point defects in n-type Bi2Te3-based materials from the perspective of thermodynamics and kinetics, in combination with positron annihilation measurement. It is found that not only the mechanical deformation but also the sintering temperature is vital to the donor-like effect. The mechanical deformation can promote the formation of cation vacancies and facilitate the donor-like effect, and the sintering process can provide excess energy for Bi antisite atoms to surmount the diffusion potential barrier. This work provides us a better understanding of the evolution law of intrinsic point defects in Bi2Te3-based alloys and guides us to control the carrier concentration by manipulating intrinsic point defects.