A combinatorial approach to microstructure and thermopower of bulk thermoelectric materials: The pseudo-ternary PbTe-Ag2Te-Sb 2Te3 system
Journal
Journal of Materials Chemistry
Journal Volume
22
Journal Issue
46
Start Page
24335
End Page
24347
ISSN
13645501
Date Issued
2012
Author(s)
Abstract
The microstructures and Seebeck coefficients of thermoelectric alloys in the pseudo-ternary PbTe-Ag2Te-Sb2Te3 system were examined using samples that were compositionally graded by unidirectional solidification by the Bridgman method and diffusion couples. At compositions near the middle of the pseudo-binary PbTe-AgSbTe2 line, a compositionally modulated microstructure has been found. From diffusion couple experiments, it is found that the PbTe-AgSbTe2 system exhibits a miscibility gap at low temperatures while it forms a complete solid solution at high temperatures; the critical temperature is between 400 °C and 450 °C. The modulated microstructure originates from the decomposition of the high-temperature solid solution during cooling. Scanning Seebeck coefficient measurement on these samples covers a wide compositional space of the pseudo-ternary system. The Seebeck coefficient transitions from positive values at AgSbTe2-rich compositions to negative values at PbTe-rich compositions on the pseudo-binary PbTe-AgSbTe2 line. Composition-graded samples prepared by the Bridgman method are thus useful to investigate thermoelectric materials in multi-component systems. © The Royal Society of Chemistry 2012.
Type
journal article