Formation of Sb2Te3 Widmanstätten precipitates in thermoelectric PbTe

• Published in: Acta materialia Vol. 57; no. 3; pp. 666 - 672
• Main Authors: IKEDA, Teruyuki, RAVI, Vilupanur A, SNYDER, G. Jeffrey
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier 01.02.2009
• Subjects: Applied sciences; Exact sciences and technology; Metals. Metallurgy; Thermoelectric materials; Precipitation; Bridgman technique; Solidification microstructure; Widmanstaetten structure; Precipitate; Microstructure; Solidification
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2008.10.005

Unidirectional solidification experiments have been performed with a thermoelectric alloy with a starting composition of Pb10.5Sb31.6Te57.9 in the pseudobinary PbTe -Sb2Te3 system. The bottom of the resulting rod consists of PbTe phase with Widmanstatten precipitates of Sb2Te3. The precipitation is due to a decrease in the solubility of Sb2Te3 with temperature: the solubility at 450 deg 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)Sb2Te3//{1 1 1}PbTe and < 1 1 0 > Sb2Te3// < 1 1 0 > PbTe was found with a maximum misorientation of 15 deg. The Seebeck coefficient after annealing at 450 deg C was -50 +/- 10 muV deg C-1 at room temperature. To improve the thermoelectric properties, tuning of the carrier concentration would be necessary.