Development and Evolution of Nanostructure in Bulk Thermoelectric Pb-Te-Sb Alloys
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Motivated by reports of exceptionally high zT > 2 in thin film superlattices or “quantum well” materials with nanometer sized features, we have undertaken a study of composite materials with nanoscale features that promise to provide similar structures in bulk material. Nanometer scale layers of PbTe and Sb2Te3 with periodicities of 180 nm to 950 nm form when quenched eutectic PbTe-Sb2Te3 melt, crystallizing as Pb2Sb6Te11, subsequently annealed. The lamellar spacing depends on the temperature and time of the anneal. The mechanism for the development of the nanostructures is probed by examining the fraction of material transformed as a function of anneal time. Preliminary analysis of the shape factor exponent reveals that the transformation to the nanostructured lamellae bears similarities to the thickening of very large plates. The coarsening of the lamellar spacing is also examined as a function of time and temperature.
KeywordsThermoelectric lamellar spacing fraction transformed coarsening
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This work was supported by the Office of Naval Research. LC was supported by the SURF program at Caltech.
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