Formation of Sb2Te3 Widmanstätten precipitates in thermoelectric PbTe

✍ Scribed by Teruyuki Ikeda; Vilupanur A. Ravi; G. Jeffrey Snyder

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 426 KB
• Volume: 57
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/j.actamat.2008.10.005

✦ Synopsis

Unidirectional solidification experiments have been performed with a thermoelectric alloy with a starting composition of Pb 10.5 Sb 31.6 Te 57.9 in the pseudobinary PbTe-Sb 2 Te 3 system. The bottom of the resulting rod consists of PbTe phase with Widmansta ¨tten precipitates of Sb 2 Te 3 . The precipitation is due to a decrease in the solubility of Sb 2 Te 3 with temperature: the solubility at 450 °C was determined to be 2.1 ± 0.2 at.% Sb. The average thickness of plates was estimated to be $100 nm. The spacings between neighboring plates has a distribution in the 200-3000 nm range, peaking around 900 nm. The habit planes of precipitation are of the {1 1 1}PbTe family. An orientation relationship of (0 0 0 1)Sb 2 Te 3 //{1 1 1}PbTe and <1 1 2 0>Sb 2 Te 3 //<1 1 0>PbTe was found with a maximum misorientation of 15°. The Seebeck coefficient after annealing at 450 °C was À50 ± 10 lV °CÀ1 at room temperature. To improve the thermoelectric properties, tuning of the carrier concentration would be necessary.