Realizing Ambipolar Transport in Bi_1‐xSb_x Through Aliovalent Alloying

Abstract Thermoelectric materials and devices are potential candidates of all‐solid‐state cooling and power generation for various applications. Most thermoelectric research works focus on room‐temperature to medium/high‐temperature range, while available materials for cryogenic temperature application are limited. N ‐type Bi‐Sb alloy is among the most promising cryogenic temperature thermoelectric materials, but a suitable p ‐type counterpart is still lacking. In this work, BiSb alloys with continuously tunable ambipolar transport are realized through aliovalent alloying with Sn, and both p ‐ and n ‐type materials suitable for cryogenic thermoelectric applications are successfully obtained. The thermodynamic competition between the impurity phase and ternary solid solution Bi 0.85 Sb 0.15‐y Sn y is investigated by first principle calculations. Electromagnetic melting and hot‐pressing methods are employed to fabricate Bi‐Sb alloys in both conduction types. The carrier polarity and concentration of Bi‐Sb alloys can be continuously regulated up to over 10 20 cm −3 via Sb and Sn content control. The n ‐type Bi 1‐x Sb x and p ‐type Bi 0.85 Sb 0.15‐y Sn y prepared in this work exhibit comparably high thermoelectric performance ≈200 K with excellent mechanical properties. This work paves the way toward the fabrication of homogeneous Bi‐Sb thermoelectric devices for cryogenic applications.