Solidification processing of alloys in the pseudo-binary PbTe-Sb2Te3 system

The effects of composition and cooling rate on the microstructures of alloys in the pseudo-binary PbTe-Sb2Te3 system were investigated as a first step towards the design of nanostructured materials with enhanced thermoelectric properties. Liquid alloys of three different compositions were cooled in three distinct ways: water quenching, air cooling and furnace cooling. The resultant structures and phases were examined by electron microscopy, electron microprobe chemical analysis and electron backscatter diffraction. The compound Pb2Sb6Te11 precipitated as a metastable phase (in conjunction with PbTe and/or Sb2Te3) under all conditions. Furthermore, whereas PbTe exhibited dendritic morphology, Sb2Te3 and Pb2Sb6Te11 I crystallized as lamellar platelets with preferred (00 1) orientation. The range of cooling rates was from similar to 1 to 26 K/s, while the characteristic microstructural feature size ranged from 10 to 35 pm for dendrites, and from 15 to 50 mu m for lamella. The prospects for achieving nanoscale structure are discussed. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.