Thermoelectric properties of sintered Bi using plasma-treated powder

Sintered Bi was prepared by using the plasma-treated powder in order to improve their thermoelectric figure of merit. Surfaces of Bi raw powder were modified in the Ar, H-2, O-2 and SbCl3 rf-plasmas prior to sintering, and Bi was sintered using the powder obtained by the spark plasma sintering. For Bi samples sintered using O-2 plasma-treared powder, the electrical conductivity sigma was increased in spite of growth of Bi oxcides, as compared with that of the untreated one. The increase in sigma is attributed to the increase in the carrier concentration. As a result, the thermoelectric figure of merit at room temperature was improved 1.5 times as high as that of the untreated one. The improvement of thermoelectric properties of sintered Bi was observed also in the case of other gas plasma treatment.