Grain-boundary engineering driven high-performance Bi–Sb–Te bulk thermoelectric materials fabricated by gas atomization and hot extrusion

Grain-boundary engineering is an effective strategy for enhancing the thermoelectric properties of Bi 2 Te 3 -based materials. Through modulating grain-boundary characteristics via a gas atomization (GA)/hot extrusion (HE) fabrication technology, a high-performance bulk (Bi 0.2 Sb 0.8 ) 2 Te 3 material with a maximum ZT (T = 300K) value of 1.43 was achieved, which is 1.79 times larger than that of mechanically alloyed (MAed)/HEed sample. Such excellent performance resulted from the satifactory Seebeck coefficient (230 μV K −1 ), electrical resistivity (10.75 μΩ m), and thermal conductivity (1.03 W m −1 K −1 ). Both theoretical calculations (density functional theory calculations and molecular dynamics simulations) and experimental characterizations indicate that the highly ordered grain-boundary structure within GAed/HEed sample facilitates carrier transport while effectively scatters phonons, which readily decouples the electrical and thermal transport. Further band structure and density of states calculations reveal that the good electrical transport properties of the highly ordered atomic structure is attributed to its lower carrier effective mass, higher carrier mobility, and better inhibition of electronic localization. Moreover, the GAed/HEed bulk material exhibit better chemical homogeneity, performance stability, and satisfactory hardness, which are promissing for industrical applications.