No abstract

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 Sb 2 Te 3 with periodicities of 180 nm to 950 nm form when quenched eutectic PbTe-Sb 2 Te 3 melt, crystallizing as Pb 2 Sb 6 Te 11 , 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.

No abstract

In analogy to recent demonstrations of enhanced thermoelectric properties in superlattice materials, composite structures with nanoscale features promise dramatic improvements in the figure of merit of thermoelectric materials. Fabrication of nanostructured thermoelectric materials via bulk synthesis is an attractive route for commercial applications. Nanometer scale lamellae of PbTe and Sb 2 Te 3 form when quenched eutectic PbTe-Sb 2 Te 3 melt is subsequently annealed. The lamellar spacing depends on the temperature and time of the anneal. The mechanism for the development of the nanostructures can be characterized by examining the fraction of material transformed as a function of anneal time. Preliminary analysis of the shape factor exponent reveals that the evolution of the nanostructured lamellae is likened to the thickening of very large plates. The coarsening of the lamellar spacing is also examined as a function of time.