Preparation and interface analyses of a P-type segmented FeSi/sub 2//Bi/sub 2/Te/sub 3/ material

Abstract

P-type segmented FeSi/sub 2//Bi/sub 2/Te/sub 3/ thermoelectric material has been prepared by the dip coating procedure using Sn/sub 95/Ag/sub 5/ as the bridge material. An apparent Seebeck coefficient of about 225 /spl mu/V/K is obtained, which is significantly higher than those of both homogeneous materials /spl beta/-FeSi/sub 2/ and Bi/sub 2/Te/sub 3/ in the same temperature range. The maximum power output of the segmented FeSi/sub 2//Bi/sub 2/Te/sub 3/ is approximately 2.5 times that of the monolithic material /spl beta/-FeSi/sub 2/ in the same temperature range. This implies that not only does the segmented material benefit from Bi/sub 2/Te/sub 3/ at the low temperature side, but it also makes fully use of the characteristics of /spl beta/-FeSi/sub 2/ at high temperature. SEM and EDAX analyses revealed that interdiffusions do to some extent exist in all interfaces. A eutectic mixture could easily be formed since its melting point is lower than the annealing temperature, which trigger the exfoliation in the interface between Sn/sub 95/Ag/sub 5/ and Bi/sub 2/Te/sub 3/ under the stress due to the thermal expansion coefficient mismatch of both materials. Although the maximum power output of the material with a Ni layer sandwiched between Sn/sub 95/Ag/sub 5/ and Bi/sub 2/Te/sub 3/ is a little lower than those of the materials without Ni layer, the thermal stability can be significantly improved.