The microstructure, liquidus projection and thermodynamic modeling of thermoelectric AgePbeTe system Hsin-jay Wu a , Wei-jian Foo b , Wojciech Gierlotka c , Sinn-wen Chen a, * , G. Jeffrey Snyder d a Department of Chemical Engineering, National Tsing Hua University, #101, Sec. 2, Kuang-Fu Rd., Hsin-Chu 300, Taiwan b Engineering Science Programme, National University of Singapore, Blk EA, #06-10, 9 Engineering Drive, Singapore 117576, Singapore c Department of Chemical Engineering and Material Science, Yuan Ze University, # 135 Yuan-Tung Road, Chungli, Taoyuan 320, Taiwan d Materials Science, California Institute of Technology,1200, California Blvd., Pasadena, CA 91125, USA highlights graphical abstract  Eight primary solidification phases are determined in the AgePbeTe ternary system.  The thermodynamic models of the AgePbeTe ternary system are devel- oped with the Calphad approach.  The AgePbeTe liquidus projection is constructed by experimental deter- mination and calculation.  A ternary eutectic has nano-scaled feature is observed consisting of Ag 5 Te 3 , Te and dotted PbTe.  Solidification paths of AgePbeTe al- loys are calculated with the thermo- dynamic and Schiel models. article info Article history: Received 25 November 2012 Received in revised form 25 April 2013 Accepted 27 May 2013 Keywords: Microstructure Thermoelectric effects Solidification Computer modeling and simulation abstract AgePbeTe is an important system in thermoelectric applications. Various AgePbeTe alloys are prepared and their microstructures are examined. The liquidus projection of ternary AgePbeTe system is deter- mined both by experimental investigations and Calphad calculations, and the results are in good agreement. There are eight primary solidification phases, Ag, g-Ag 2 Te, b-Ag 2 Te, Ag 1.9 Te, Ag 5 Te 3 , Te, PbTe and Pb, including a miscibility gap extended from the AgeTe side. A ternary-eutectic reaction, L ¼ PbTe þ Te þ Ag 5 Te 3 , was determined with a liquid composition of Ag-4.3at%Pb-62.6at%Te at 337  C. A nanoscale microstructure containing a dotted PbTe and a lamellar matrix of Ag 5 Te 3 and Te phases results from the ternary eutectic reaction. The solidification paths of selective ternary AgePbeTe alloys are calculated using the Scheil model with the optimized interaction parameters obtained in this study, and the results are consistent with the experimental observations. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Thermoelectric materials (TE) have been extensively studied, because of their ability to directly conversion of thermal energy into electricity [1e5]. The figure of merit, zT ¼ (S 2 /rk)T, is used to evaluate the performance of a thermoelectric material, where S is the See- beck coefficient, r is the electrical resistivity, k is the thermal con- ductivity, and T is the absolute temperature. The ternary AgePbeTe system is recognized as an important thermoelectric system, because it is a constituent system of the extensively studied Ag 2 Tee PbTe system [6,7]. It is also highlighted by containing a PbTe com- pound [8,9] that shows remarkable thermoelectric potential. * Corresponding author. E-mail addresses: swchen@mx.nthu.edu.tw, swchen@che.nthu.edu.tw (S.-w. Chen). Contents lists available at SciVerse ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys 0254-0584/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matchemphys.2013.05.072 Materials Chemistry and Physics xxx (2013) 1e10 Please cite this article in press as: H.-j. Wu, et al., The microstructure, liquidus projection and thermodynamic modeling of thermoelectric Age PbeTe system, Materials Chemistry and Physics (2013), http://dx.doi.org/10.1016/j.matchemphys.2013.05.072