High thermoelectric figure of merit ZT in PbTe and Bi2Te3-based superlattices by a reduction of the thermal conductivity

Experimental evidence is presented for an enhanced thermoelectric figure of merit ZT = sigmaS(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 Bi2Te3-superlattices (SLs) parallel to the layer planes. Data on thermoelectric properties of Bi2Te3/Bi-2,(SexTe1-x)(3)-SLs. of PbTe-based doping SLs, and PbTe/PbSe0.2Te0.8-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 sigmaS(2) in the SLs in total an enhancement of the figure of merit ZT is found in these highly-doped PbTe and Bi2Te3-based SLs. (C) 2002 Elsevier Science B.V. All rights reserved.