Thermoelectric properties of intermetallic compounds: Mg₃Bi₂and Mg₃Sb₂ for medium temperature range thermoelectricelements

T. Kajikawa, N. Kimura, T. Yokoyama

Shonan Institute of Technology, 1-1-25 Tsujido-nishikaigan,Fujisawa, Kanagawa 251-8511 Japan

Hot-presssintered thermoelectric elements of intermetallic compounds: Mg₃Bi₂and Mg₃Sb₂ were examined for the feasibility as mediumtemperature range thermoelectric elements, which belong to the family ofzincblende crystal structure. The experiments were carried out varying thesintering temperature in order to find out the optimum morphology for thesintered material system, because the thermoelectric performance was affected withthe macro- and micro-structure due to the sintering process. Seebeckcoefficients (S), electrical conductivity (s) and thermalconductivity (l) weremeasured in the temperature range from 300K to 773K. According to the Seebeckcoefficient measurement, both materials were p-type semiconductor. As theresults, the power factor (=S² s) could be obtained from1.0x10^-3 W/m²K at 550K to 2.5x10^-3 W/m²Kat 773K for Mg₃Bi₂ system ,and from 1.0x10^-3W/m²K at 600K to 2.0x10^-3 W/m²K at 740K for Mg₃Sb₂system respectively. The measurement of thermal conductivity by laser flashmethod showed that the hot-press sintered Mg₃Sb₂ elementhad the relatively low thermal conductivity. The preliminary estimate for Mg₃Sb₂elements promisingly shows the non-dimensional figure of merit ZT of 0.55 at660K.