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.