Thermoelectric properties of intermetallic compounds: Mg/sub 3/Bi/sub 2/ and Mg/sub 3/Sb/sub 2/ for medium temperature range thermoelectric elements

Hot-press sintered thermoelectric elements of intermetallic compounds: Mg/sub 3/Bi/sub 2/ and Mg/sub 3/Sb/sub 2/ were examined for the feasibility as medium temperature range thermoelectric elements, which belong to the family of zinc blend crystal structure. The experiments were carried out varying the sintering temperature in order to find out the optimum morphology for the sintered material system, because the thermoelectric performance was affected with the macro- and micro-structure due to the sintering, process. Seebeck coefficients (S), electrical conductivity (/spl sigma/) and thermal conductivity (/spl kappa/) were measured in the temperature range from 300K to 773K. According to the Seebeck coefficient measurement, both materials were p-type semiconductor. As the results, the power factor (=S/sup 2//spl sigma/) could be obtained from 1.0x10/sup -3/ W/m/sup 2/K at 550K to 2.5x10/sup -3/ W/m/sup 2/K at 773K for Mg/sub 3/Bi/sub 2/ system and from 1.0x10/sup -3/ W/m/sup 2/K at 600K to 2.0x 10/sup -3/ W/m/sup 2/K at 740K for Mg/sub 3/Sb/sub 2/ system respectively. The measurement of thermal conductivity by laser flash method showed that the hot-press sintered Mg/sub 3/Sb/sub 2/ element had the relatively low thermal conductivity. The estimate for Mg/sub 3/Sb/sub 2/ elements promisingly shows the dimensionless figure of merit ZT of 0.55 at 660K.