Ikeda, Teruyuki and Marolf, Nathan J. and Bergum, Kristin and Toussaint, Marcus B. and Heinz, Nicholas A. and Ravi, Vilupanur A. and Snyder, G. Jeffrey (2011) Size control of Sb_2Te_3 Widmanstätten precipitates in thermoelectric PbTe. Acta Materialia, 59 (7). pp. 2679-2692. ISSN 1359-6454 http://resolver.caltech.edu/CaltechAUTHORS:20110421-104603452
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The number density and area per unit volume of Sb_2Te_3 Widmanstätten plates in thermoelectric PbTe were controlled through two types of heat treatments of (PbTe)_(1−x)-(Sb_2Te_3)_x, where x = 0.04 and 0.06: isothermal annealing at various temperatures and cooling from a solid-solution regime to a two-phase region with various rates. The microstructure was quantified by image analysis of scanning electron micrographs and Rietveld refinements of X-ray diffraction profiles. Isothermal annealing of (PbTe)_(0.94)-(Sb_2Te_3)_(0.06), results in increasing number density and area per volume of precipitates with decreasing temperature. In controlled cooling rate experiments, faster cooling rates or smaller x result in higher number density and area per volume. These trends are discussed using phase transformation theories. Overall the number density and area per volume of precipitates were controlled in the ranges from 0.4 to 44 μm^(−3) and from 0.5 to 1.8 μm^(−1), respectively. Isothermal annealing was performed for time periods from 10 to 166 h at 723 K to check the stability of the microstructure at the (PbTe)_(0.94)-(Sb_2Te_3)_(0.06) composition. While the Boyd and Nicholson model of the Greenwood–Lifshitz–Slyozov–Wagner theory for the average diameter of plates gives a reasonable value for peripheral interfacial energy, the time dependence was found to decelerate more than the t^(1/3) rule. It has also been found that the coarsening mechanism involves the elongation of plates.
|Additional Information:||© 2011 Acta Materialia Inc. Published by Elsevier Ltd. Received 2 September 2010; revised 4 December 2010; accepted 2 January 2011. Available online 4 February 2011. This work was funded by the PRESTO program (PRESTO: Precursory Research for Embryonic Science and Technology) of Japan Science and Technology Agency. M.B.T was supported by the National Science Foundation Summer Program in Solid State Chemistry under Grant no. DMR-0804648. Microscopy facilities are supported by NSF CSEM MRSEC at Caltech.|
|Subject Keywords:||Nanostructured materials; Precipitation kinetics; Thermoelectric materials; Scanning electron microscopy; Image analysis|
|Official Citation:||Teruyuki Ikeda, Nathan J. Marolf, Kristin Bergum, Marcus B. Toussaint, Nicholas A. Heinz, Vilupanur A. Ravi, G. Jeffrey Snyder, Size control of Sb2Te3 Widmanstatten precipitates in thermoelectric PbTe, Acta Materialia, Volume 59, Issue 7, April 2011, Pages 2679-2692, ISSN 1359-6454, DOI: 10.1016/j.actamat.2011.01.006. (http://www.sciencedirect.com/science/article/B6TW8-523JY3H-3/2/ef1eda085d2df9810c165d9060db5ca7)|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||21 Apr 2011 18:27|
|Last Modified:||21 Apr 2011 18:27|
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