Optimizing thermoelectric properties: Microstructure analysis of Ag1-xPb18Sb1+yTe20

The feasible recovery of waste-heat energy as it is generated by industrial and vehicle engines has led to increasing research interest in thermoelectrics (TE). In order to get TE materials with high performance, i.e. with a large figure of merit ZT, one needs to tune electronic and phononic properties. A promising candidate is the quaternary compound Ag1-xPb18Sb1+yTe20 (Lead-Antimony-Silver-Tellurium, LAST) for applications in the mid-temperature range. While the self-organized nanostructures assumed to act as phonon scatterers decrease the lattice thermal conductivity κL, the volume fraction of Sb and Ag and their ratio in the matrix have a significant influence on the electronic properties of the material. This study reports microstructure investigations at the micrometer and nanometer scale regarding SEM and TEM analysis, as well as measurements concerning TE properties. An attempt is made to derive a structure-property relationship.