Sima Aminorroaya Yamini : Lead-chalcogenide thermoelectric materials

Lead (Pb) chalcogenides have received considerable attention amongst existing thermoelectric materials due to their relatively high conversion efficiencies for both n-type and p-type compounds. Tremendous efforts have been devoted to reduce the lattice thermal conductivity of their bulk materials by nanostructuring. Multiphase nanostructured compounds exhibit higher thermoelectric efficiency than those of their constituent phases. Our results on a Na-doped multiphase quaternary system of (PbTe)_0.65(PbS)_0.25 S(PbSe)_0.1 show a conversion efficiency (zT) value of ~2 in a heavily doped sample. The observed partitioning of charge carriers (sodium) in our recent studies suggests that the achieved large zT is attributed to the heterogeneous distribution of the sodium dopant between the matrix and precipitates and its redistribution at elevated temperatures . Our detailed atom probe tomography (APT) analysis quantified this heterogeneity at room temperature, and in-situ hot stage transmission electron microscopy (TEM) and high-resolution neutron powder diffraction show the dissolution of precipitates at the temperature of applications. These findings can lead to further advances in designing and characterizing high performance multiphase thermoelectric materials.