Microstructure analyses and thermoelectric properties of Ag1-xPb18Sb1+yTe20

This study reports microstructural investigations of long-term annealed 18, x=y=0, hereinafter referred to as AgPb18SbTe20) (Lead-Antimony-Silver-Tellurium, LAST-18) as well as of Ag1-xPb18Sb1+yTe20, i.e. Ag-deficient and Sb-excess LAST-18 (x not equal 0, y not equal 0), respectively. Two different length scales are explored. The micrometer scale was evaluated by SEM to analyze the volume fraction and the number of secondary phases as well as the impact of processing parameters on the homogeneity of bulk samples. For AgPb18SbTe20, site-specific FIB liftout of TEM lamellae from thermoelectrically characterized samples was accomplished to investigate the structure on the nanometer scale. High-resolution TEM and energy-filtered TEM were performed to reveal shape and size distribution of nanoprecipitates, respectively. A hypothesis concerning the structure-property relationship is set out within the frame of a gradient annealing experiment. This study is completed by results dealing with inhomogeneities on the micrometer scale of Ag1-xPb18Sb1+yTe20 and its electronic properties. (C) 2012 Elsevier Inc. All rights reserved.