High thermoelectric figure of merit ZT in PbTe and Bi/sub 2/Te/sub 3/-based superlattices by a reduction of the thermal conductivity

Experimental evidence is presented for an enhanced thermoelectric figure of merit ZT = sigma S/sup 2/T/ lambda (where sigma is the electrical conductivity, S the thermopower, T the temperature, and lambda is the thermal conductivity) by a reduction of the thermal conductivity lambda in PbTe- and Bi/sub 2/Te/sub 3/-superlattices (SLs) parallel to the layer planes. Data on thermoelectric properties of Bi/sub 2/Te/sub 3//Bi/sub 2/(Se/sub x/Te/sub 1-x/)/sub 3/-SLs, of PbTe-based doping SLs, and PbTe/PbSe/sub 0.2/Te/sub 0.8/-SLs are presented. In these structures, a decrease of lambda was measured compared to the corresponding bulk compounds or homogeneous alloys. Despite a drop of the total power factor sigma S/sup 2/ in the SLs in total an enhancement of the figure of merit ZT is found in these highly-doped PbTe and Bi/sub 2/Te/sub 3/-based SLs.