Characterization of dry milled powders of LAST (lead–antimony–silver–tellurium) thermoelectric material

Abstract

Although thermoelectric (TE) materials are often fabricated as cast ingots, there has been recent interest in the powder processing of these materials. Cast TE materials typically have grain sizes as large as several hundred microns, but powder processing (grinding, milling and then sintering) can produce dense specimens with a reduced grain size, an improved mechanical integrity and enhanced TE properties. In the TE literature when powder processing is employed, little or no description is provided of the powder processing techniques and the powder processing parameters are either not characterized or only a mean particle size is given. In this study, powders milled from solid cast ingots of the TE compound LAST (lead–antimony–silver–tellurium) were characterized via Coulter Counter, to measure the mean powder particle size and the size distribution, scanning electron microscopy (SEM), to examine the powder particle morphology, and X-ray diffraction (XRD), to detect possible phase changes or amorphization. The impurity levels in the milled powders were examined by wear rate measurements on the milling media, as well as by energy dispersive X-ray analysis and inductively coupled plasma measurements.

Acknowledgements

This study is supported by the US Department of Energy Grant DE-FC26-04NT42281 and Office of Naval Research MURI Grant number N000140310789. The authors acknowledge the use of scanning electron microscope facility at the Advanced Microscopy Center, Michigan State University. The authors also acknowledge helpful conversations with Prof. M. G. Kanatzidis of Northwestern University. In addition, the authors acknowledge the assistance of Mr. Bradley Hall, Michigan State University, with the ICP measurements.

Notes

¶Current address: Materials Science and Engineering Department, Ohio State University, Columbus, OH 43210, USA.

Additional information

Notes on contributors

A. L. Pilchak¶

¶Current address: Materials Science and Engineering Department, Ohio State University, Columbus, OH 43210, USA.