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=σS2T/λ (where σ is the electrical conductivity, S the thermopower, T the temperature, and λ is the thermal conductivity) by a reduction of the thermal conductivity λ in PbTe- and Bi2Te3-superlattices (SLs) parallel to the layer planes. Data on thermoelectric properties of Bi2Te3/Bi2(SexTe1−x)3-SLs, of PbTe-based doping SLs, and PbTe/PbSe0.2Te0.8-SLs are presented. In these structures, a decrease of λ was measured compared to the corresponding bulk compounds or homogeneous alloys. Despite a drop of the total power factor σS2 in the SLs in total an enhancement of the figure of merit ZT is found in these highly-doped PbTe and Bi2Te3-based SLs.