Compositional Sensitivity of Microstructures and Thermoelectric Properties of Ag1-x Pb18Sb1+y Te20 Compounds

This study reports microstructural investigations of Ag1-x Pb18Sb1+y Te-20, i.e., Ag-deficient and Sb-excess lead-antimony-silver-tellurium-18 (LAST-18: x not equal 0, y not equal 0). Two different length scales are explored. The micrometer scale was evaluated by scanning electron microscopy (SEM) to analyze the number of secondary phases as well as composition. Site-specific focused ion-beam liftout of transmission electron microscopy (TEM) lamellae from thermoelectrically characterized samples was accomplished to investigate the structure on the nanometer scale. TEM was performed to reveal the shape and orientation relationship of nanoprecipitates. The study is completed with results for the thermoelectric properties for different values of x and y.