Large scale production of high efficient and robust p type Bi Sb Te based thermoelectric materials by powder metallurgy
Abstract Development of large scale high performance thermoelectric materials is one of the challenges in thermoelectric energy conversion. We have successfully fabricated large scale production (3 5 kg/min) of bismuth antimony telluride (Bi Sb Te) alloys by gas atomization (GA) and achieved a high figure of merit (ZT) value over unity (1) at 350 K. To get more performance from thermoelectric materials, we controlled the grain size of GA powders via mechanical milling (GA MA) and consolidated the resultant nano powder by spark plasma sintering. The ZT values of GA MA samples were greatly improved (15% over those of GA bulk due to shifting control of their grain size from micron order to submicron order. The improved ZT values are due to the suppression of lattice thermal conductivity, which was drastically decreased due high scattering of phonons at numerous grain boundaries and twin boundaries. The mechanical properties were greatly improved (GA MA sample hardness improved 61% over the GA sample) which would provide impressive benefits for device fabrication and practical applications for thermoelectric energy conversion.