High thermoelectric performance of mechanically robust n-type Bi2Te3-xSex prepared by combustion synthesis

The traditional zone melting (ZM) method for fabricating Bi2Te3-based thermoelectric materials has long been considered a time and energy intensive process. Here, a combustion synthesis called the self-propagating high-temperature synthesis (SHS) is employed to synthesize Bi2Te3-based thermoelectric materials. Thermodynamic and kinetic parameters of the SHS process relevant to Bi2Te3 and Bi2Se3 were systematically studied for the first time. SHS combined with plasma activated sintering (PAS) results in a single-phase homogeneous material with precisely controlled composition, no preferential orientation, high thermoelectric performance, and excellent mechanical properties. The technologically relevant average ZT value of SHS-PAS Bi2Te2.4Se0.6 from 298 to 523 K is 0.84, which is an increase of about 25% compared with the ZM sample. The compressive strength and the bending strength of SHS-PAS Bi2Te2.4Se0.6 are increased by nearly 250% and 30%, respectively, compared with those of the ZM samples, measured perpendicular to the c-axis. Moreover, the SHS-PAS process is very fast and shortens the synthesis time from tens of hours to 20 min. On account of the simplicity of the process, short synthesis time, minimal use of energy, and the scalability of the method, SHS-PAS technology provides a new and efficient method for large-scale, economical fabrication of Bi2Te3-based compounds.