Enhanced thermoelectric properties of n-type Bi2Te2.7Se0.3 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 Bi2Te2.7+xSe0.3 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 Bi2Te2.7Se0.3 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 Bi2Te2.71Se0.3, indicating potential for thermoelectric power generation (below 500 K).