Mechanically enhanced p- and n-type Bi2Te3-based thermoelectric materials reprocessed from commercial ingots by ball milling and spark plasma sintering

Abstract

Abstract Ball milling (BM) combined with spark plasma sintering (SPS) is increasingly used for fabricating high-performance thermoelectric materials. This work was conducted to clarify the effects of BM and SPS on the electrical transport and thermoelectric properties of both p - and n -type Bi 2 Te 3 based materials using commercially available p -type (Bi,Sb) 2 Te 3 and n -type Bi 2 (Se,Te) 3 ingots. Interestingly, it is found that BM and SPS differently affected the electrical properties of p - and n -type Bi 2 Te 3 -based thermoelectric materials; the dimensionless thermoelectric figure of merit ( ZT ) increases in p -type Bi 0.5 Sb 1.5 Te 3 but decreases somewhat in n -type Bi 2 Te 2.7 Se 0.3 after BM and SPS. Hall experiments reveal the reason for this difference. Both p -type and n -type sintered materials show 2–3 times higher mechanical strength than the ingots because of microstructure refinement effect, which has been measured by using a small-sized biaxial bending test. The improved mechanical properties are in favor for device fabrication.