Plasticity of Bi₂Te₃-family thermoelectric crystals

The exceptional plasticity discovered most recently in defective Bi₂Te₃ bulk crystal inspires the great interest on investigating the plasticity of other Bi₂Te₃-family bulk crystals. In this work, Bi₂Se₃, Sb₂Te₃, and their solid solutions with Bi₂Te₃ are grown by the temperature gradient method to comprehensively clarify the relationship among chemical composition, native defect, microstructure, and plasticity of Bi₂Te₃-family compounds. Compared with Bi₂Te₃ bulk crystal, Bi₂Se₃ and Sb₂Te₃ bulk crystals exhibit poorer plasticity at room temperature. The origin is attributed to the lack of substantial antisite defects in Bi₂Se₃ and Sb₂Te₃ alike that in Bi₂Te₃, which impedes the formation of the high-density, diverse microstructures. Alloying either Se or Sb in Bi₂Te₃ modifies the native defects and microstructures and thus changes plasticity and thermoelectric performance. Finally, the composition range for the Bi₂(Te,Se)₃ and (Bi,Sb)₂Te₃ bulk crystals that simultaneously possess exceptional plasticity (maximum bending strain >10%) and thermoelectric performance is determined.