An in situ SEM experimental study of the thermal stability of a LAST thermoelectric material

Abstract

Thermal stability is a requirement for the deployment of thermoelectric (TE) materials in the application of power generation. Lead–antimony–silver–tellurium (LAST) is an emerging material with promising TE properties. This study focuses on the thermal stability of a LAST sample with composition Ag_0.86Pb₁₉SbTe₂₀ fabricated from a cast ingot. Using a customized heating stage, the morphology of the LAST particles was studied via scanning electron microscopy (SEM) in situ, between room temperature and 848 K. The material was found to be stable below 823 K. The inclusion phase, which was antimony-rich, had a lower thermal stability than the PbTe-rich matrix. SEM findings were consistent with the results of a thermogravimetric analysis. The results from an in situ heating study suggest that protective environments should be used during the processing and application of LAST materials.

Keywords:

• thermoelectric
• thermal stability
• microstructure change
• SEM

Acknowledgements

The authors acknowledge the financial assistance of the Office of Naval Research MURI Grant number N000140310789 and the US Department of Energy Grant DE-FC26-04NT 42281. The research through the Oak Ridge National Laboratory's High Temperature Materials Laboratory User Program (proposal number 2008-033) was sponsored by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program. They also thank Mr Edward Timm at Mechanical Engineering Department of Michigan State University for processing the ingot materials used in this study and Dr A. Schindler at the Application Laboratories of Netzsch Co. for performing the TGA measurements.