Macroscopic thermoelectric inhomogeneities in (AgSbTe 2) x (PbTe) 1-x

Abstract

Exceptionally high thermoelectric figure of merit (zT>2), has been reported for (Ag1-y Sb Te2) 0.05 (PbTe)0.95, which may involve the nanoscale microstructure. However, conflicting reports on the same materials claim only zT of 1 or less. Here we show that (Ag1-y Sb Te2) 0.05 (PbTe)0.95 materials are multiphase on the scale of millimeters despite appearing homogeneous by x-ray diffraction and routine electron microscopy. Using a scanning Seebeck microprobe, we find significant variation of Seebeck coefficient (including both n -type and p -type behavior in the same sample) that can explain the discrepancy in reported zT. More homogeneous samples can be prepared with faster cooling rates. © 2005 American Institute of Physics.