(Bi,Sb) 2 Te 3 -PbTe chalcogenide alloys: Impact of the cooling rate and sintering parameters on the microstructures and
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Thomas Jürgen Institute of Complex Materials, IFW Dresden, D–01069 Dresden, Germany
Joachim Schumann Institute for Solid State Research, IFW Dresden, D–01069 Dresden, Germany
Martin Jägle and Harald Böttnerb) Fraunhofer Institute for Physical Measurement Technique, D–79110 Freiburg, Germany
Thomas Gemming Institute of Complex Materials, IFW Dresden, D–01069 Dresden, Germany
Jürgen Schmidt Fraunhofer-Institut für Fertigungstechnik und Angewandte Materialforschung IFAM, Institutsteil Dresden, 01277 Dresden, Germany
Dirk Ebling Fachhochschule Düsseldorf, Forschung und Transfer Präsidium, D-40225 Düsseldorf, Germany (Received 11 December 2010; accepted 28 February 2011)
(Bi,Sb)2Te3 + 4 mol%PbTe was quenched in water and on a rotating copper wheel (melt spinning). It was found that PbTe was immiscible in (Bi,Sb)2Te3 when the material is quenched in water and that the thermoelectric figure of merit increases by annealing. Natural nanostructures (nns) were found in melt-spun (Bi,Sb)2Te3, whereas they were hard to detect in (Bi,Sb)2Te3 alloyed with PbTe. There is a correlation between the orientation of the strain field and the nns. Within the grains of melt-spun (Bi,Sb)2Te3 alloyed with PbTe, the chemical composition was homogeneous. An enrichment of Pb was found at the grain boundaries. Quenched (Bi,Sb)2Te3 alloyed with 0.3 wt%PbTe have been spark plasma sintered (SPS). After optimization, the Seebeck coefficients of the melt-spun SPS (MS-SPS) materials were larger than for materials quenched in water and sintered (QW-SPS) materials. In addition, the mobility increases with the carrier concentration in MS-SPS materials, whereas it decreases in QW-SPS materials.
I. INTRODUCTION AND BACKGROUND
Thermoelectric converters based on the Seebeck and Peltier effects enable the direct transformation of heat into electricity and solid-state refrigeration. While solar panels convert light into electricity, thermoelectric devices can make use of waste heat and be used as heat pump as well. They are compact and maintenance free. The range of applications of thermoelectric devices is potentially very broad, e.g., for converting exhaust gas into electricity, to refresh car passengers instead of the whole a)
Address all correspondence to this author. e-mail: [email protected] b) This author was an editor of this focus issue during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs. org/jmr-editor-manuscripts/ DOI: 10.1557/jmr.2011.78 J. Mater. Res., Vol. 26, No. 15, Aug 14, 2011
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car, or simply to maintain laser source or battery to their optimal operating temperature. It is, therefore, not surprising that thermoelectric science and technology has found a renewal of interest because they are contributing to build a more energy-efficient society.1 However, only about 6% of wasted heat could be actually converted to electricity with thermoelectric devices, the limiting fac
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