Enhanced thermoelectric properties of n-type Bi₂Te_2.7Se_0.3 for power generation

The abundant waste heat (below 500 K) from industry and automobile exhaust stimulate the development of thermoelectric materials for power generation. The commercial Bi₂Te₃-based alloys are generally used near room temperature. Herein, n-type Bi₂Te_2.7+xSe_0.3 was prepared by a method of mechanical alloying combined with hot pressing, which is more efficient, time-saving, and energy-saving than the method of melting and spark plasma sintering. The n-type Bi₂Te_2.7Se_0.3 being suitable for power generation (below 500 K) is obtained by manipulating the intrinsic point defects to enhance carrier concentration and suppress the intrinsic excitation at elevated temperature using a tiny amount of excess Te. Enhanced carrier concentration improves electrical conductivity, while enhanced phonon scattering reduces lattice thermal conductivity, originating from increased anti-site defects Te^._Bi in Te-rich condition. Consequently, the enhanced ZT peak gradually shifts to higher temperature while increasing the excess Te content. The maximum ZT peak of 0.9 at 373 K and an average ZT of 0.82 between 300 and 498 K are obtained in Bi₂Te_2.71Se_0.3, indicating potential for thermoelectric power generation (below 500 K).