High ZT Value and Ultralow Lattice Thermal Conductivity Induced by Edge Dislocations Coupled with the Superlattice Structure in Ag-Doped BST Alloy

This study investigates the effect of Ag doping on the thermoelectric properties of the BiSbTe3 (BST) alloy. High-quality BST alloys were prepared by using the NaCl solvent method, and the most promising BST(NaCl)(6 )sample was chosen for Ag doping experiments. The experimental results demonstrate that Ag doping significantly enhances the crystal quality and density of the alloy, leading to increased material mobility, reduced resistivity, and improved power factor. Ag doping also introduces numerous edge dislocations to the material. Additionally, highly doped samples contain Ag2Te and BST superlattice structures, which further intensify the scattering of heat transfer phonons, consequently decreasing the lattice thermal conductivity significantly. The highly Ag doped samples exhibit a remarkably low lattice thermal conductivity, reaching as low as 0.3 W m(-1) K-1 at 375 K. These modifications greatly enhance the thermoelectric efficiency of the Ag-doped samples, leading to increased ZT values. Particularly, samples with an Ag doping level of x = 0.01 exhibit a maximum ZT value of 1.38 at 425 K, and an average ZT value of 1.2 within the temperature range of 300-450 K. These findings underscore the wide-ranging application potential of Ag-doped BiSbTe3 alloys in room-temperature refrigeration and power generation. The study provides crucial insights into the characteristics of Ag-doped BiSbTe3 alloys while also contributing to the optimization of thermoelectric material design and the advancement of sustainable energy conversion technologies.