Advanced Physical Research

This study investigates the effect of high-dose gamma irradiation on the structural evolution and thermoelectric performance of nanostructured Bi₂Te₃. Structural and morphological changes were analyzed using X-ray diffraction (XRD) and atomic force microscopy (AFM), enabling a direct comparison between pristine and irradiated samples. AFM results reveal pronounced surface restructuring after irradiation, including the formation of nanoislands with lateral sizes of about 20 nm and heights of ~35 nm,  along with an increase in surface roughness. XRD analysis shows peak broadening, slight peak shifts, and the emergence of additional reflections, indicating lattice distortion, crystallite size reduction, and the formation of Te-rich secondary phases. These irradiation-induced structural modifications lead to noticeable changes in thermoelectric transport properties. The electrical conductivity remains anisotropic; however, the anisotropy ratio decreases from 3.76 to approximately 3.2 due to enhanced carrier scattering and partial disruption of in-plane transport pathways. The Seebeck coefficient remains negative, confirming n-type conduction, while its magnitude increases slightly (from −112 to −126 μV·K⁻¹), which is attributed to energy filtering effects at defects and nanoisland interfaces. In addition, the increased defect density enhances phonon scattering, which is expected to reduce lattice thermal conductivity. As a result of these combined effects, the thermoelectric performance improves after irradiation, with the figure of merit increasing from ZT ≈ 0.56 to approximately 0.60 at 450 K. These findings demonstrate that gamma irradiation may serve as a promising approach for defect engineering and nanoscale tuning of thermoelectric materials.