Evolution of point defects in Bi2Te3-based materials and performance of thermoelectric modules subjected to γ-irradiation

Bismuth telluride (Bi2Te3), renowned for its exceptional thermoelectric (TE) properties near room temperature, is used in extreme environments such as deep space exploration, leading to extensive attention on the radiation-induced defects to Bi2Te3. However, the evolution of point defects during gamma (gamma)-irradiation is still poorly understood. In this paper, we report the evolution of point defects in Bi2Te3 materials subjected to varying doses of gamma-irradiation and their impact on TE performance. Precisely, Bi0.5Sb1.5Te3 and Bi2Te2.7Se0.3 materials, along with TE modules, were fabricated and subsequently subjected to gamma-irradiation. The segregation of Te elements in Bi2Te3 was observed under low irradiation dose, attributing to the formation of interstitial atom-vacancy pair of Te induced by gamma-irradiation. In addition, the formation of point defects has a positive relation with the irradiation dose. The positron annihilation (PA) measurements revealed that the number of vacancies in Bi2Te3 diminished with increasing irradiation dose. The accompanying changes in carrier concentration (n(H)) and mobility (mu(H)) suggest that gamma-ray drives Bi atoms to occupy Te vacancies, forming antisite defects. The TE performance of Bi2Te3 was subsequently evaluated, and the findings revealed a strong correlation with the evolution of point defects. This study provides insights into the damage mechanisms and property alterations of Bi2Te3 materials under gamma-irradiation.