| Abstract |
Recent x-ray total scattering studies have suggested that Pb is off-center along the 100 direction in the well studied themoelectric material PbTe. This talk presents an EXAFS study of PbTe and Tl doped PbTe to determine if Pb or Te are off-center. Specifically EXAFS provides sensitive phase information which allow for a distinction between a split-peak for the Pb-Te distribution, which would be indicative of off-center Pb, and a thermally broadened peak. We find no evidence for a split peak for Pb-Te or Te-Pb. At 300 K, the vibration amplitude for Pb-Te (or Te-Pb) is large; this thermally-induced disorder is indicative of weak bonds, and the large disorder is consistent with the low thermal conductivity at 300 K. We also find evidence of an anharmonic potential for the nearest Pb-Te bonds, consistent with other authors. The consequences of these results will be discussed. |
