Effect of process parameters of microwave activated hot pressing on the microstructure and thermoelectric properties of Bi2Te3-based alloys

Abstract In this paper, fine-grained and highly dense n-type Bi 2 Te 2.7 Se 0.3 alloys were prepared via mechanical alloying and a new molding technology named microwave activated hot pressing (MAHP) with relatively low sintering temperature and short holding time. The effects of sintering temperature and holding time on the microstructure and thermoelectric properties of sintered samples were investigated in detail. The results indicated that the sintered alloys could achieve nearly complete densification. Laminated microstructure dominated in the as-MAHPed samples and their size increased gradually with increasing sintering temperature. At the same time, although Seebeck coefficients decreased slightly, their power factors increased obviously due to the drastic decrease of electrical resistivities. And a maximum power factor of 1.81 × 10 − 3  W m − 1  K − 2 was achieved at room temperature for the sample sintered at 693 K for 10 min. A minimum thermal conductivity of 0.61 W m − 1  K − 1 was obtained for the sample sintered at 533 K for 10 min owing to the drastic boundary-phonons scattering effect. A highest ZT value of 0.71 was obtained around 423 K for the Bi 2 Te 2.7 Se 0.3 sample sintered at 613 K without holding time. It confirms that the MAHP technology introduced here can achieve low temperature and rapid sintering process well in preparations of Bi 2 Te 3 -based alloys, and has widely potential applications in other functional materials.