Microscale Seebeck Scanning of Polycrystalline Samples of N-Type AgPb18SbTe20 and P-Type AgPb9Sn9SbTe20

We prepared polycrystalline-sintered samples of n-type AgPb18SbTe20 and p-type AgPb9Sn9SbTe20 and performed the microscale Seebeck scanning examination under room temperature conditions. Despite both samples appeared to be homogeneous by Energy Dispersive X-ray (EDX) and X-ray Diffraction (XRD) analyses, both samples contained apparently a microscale distribution of the Seebeck coefficient as observed by Seebeck microprobe analysis. The degree of the Seebeck coefficient distribution became larger in the order of PbTe, AgPb18SbTe20, and AgPb9Sn9SbTe20, indicating that an increase in the number of compositional elements of the materials led to a broader distribution of the Seebeck coefficient values. The statistical analysis of the Seebeck coefficient distribution of p-type AgPb9Sn9SbTe20 indicated a homogeneous phase seemed to appear only at the lowest Seebeck coefficient values (slightly above 50 (mu)V/K).