Improved Bulk Materials with Thermoelectric Figure‐of‐Merit Greater than 1: Tl10–xSnxTe6 and Tl10–xPbxTe6. Issue 14 (26th May 2014)

• Record Type: Journal Article
• Authors: Guo, Quansheng; Assoud, Abdeljalil; Kleinke, Holger
• Is Part Of: Advanced energy materials. Volume 4:Issue 14(2014)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2014-05-26
• Subjects: Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.201400348
• Languages: English
• ISSNs: 1614-6832

Abstract

<abstract abstract-type="main" xml:lang="en"> <title> <x xml:space="preserve">Abstract</x> </title> <p>Noting the steadily worsening problem of depleted fossil fuel sources, alternate energy sources have become increasingly important; these include thermoelectrics, which may use waste heat to generate electricity. To be economically viable, the thermoelectric figure‐of‐merit, <italic>zT</italic>, which is related to the energy conversion efficiency, needs to be in excess of unity (<italic>zT</italic> > 1). Tl<sub>4</sub>SnTe<sub>3</sub> and Tl<sub>4</sub>PbTe<sub>3</sub> were reported to attain a thermoelectric figure‐of‐merit <italic>zT</italic><sub>max</sub> = 0.74 and 0.71, respectively, at 673 K. Here, the thermoelectric properties of both materials are presented as a function of <italic>x</italic> in Tl<sub>10–<italic>x</italic></sub>Sn<sub><italic>x</italic></sub>Te<sub>6</sub> and Tl<sub>10–<italic>x</italic></sub>Pb<sub><italic>x</italic></sub>Te<sub>6</sub>, with <italic>x</italic> varying between 1.9 and 2.05, culminating in <italic>zT</italic> values in excess of 1.2. These materials are charge balanced when <italic>x</italic> = 2, according to (Tl<sup>+</sup>)<sub>8</sub>(Sn<sup>2+</sup>)<sub>2</sub>(Te<sup>2−</sup>)<sub>6</sub> and (Tl<sup>+</sup>)<sub>8</sub>(Pb<sup>2+</sup>)<sub>2</sub>(Te<sup>2−</sup>)<sub>6</sub> (or: (Tl<sup>+</sup>)<sub>4</sub>Pb<sup>2+</sup>(Te<sup>2−</sup>)<sub>3</sub>). Increasing <italic>x</italic> causes an increase in valence electrons, and thus a decrease in the dominating p‐type charge carriers. Larger <italic>x</italic> values occur with a smaller electrical conductivity and a larger Seebeck coefficient. In each case, the lattice thermal conductivity remains under 0.5 W m<sup>−1</sup> K<sup>−1</sup>, resulting in several samples attaining the desired <italic>zT</italic><sub>max</sub> > 1. The highest values thus far are exhibited by Tl<sub>8.05</sub>Sn<sub>1.95</sub>Te<sub>6</sub> with <italic>zT</italic> = 1.26 and Tl<sub>8.10</sub>Pb<sub>1.90</sub>Te<sub>6</sub> with <italic>zT</italic> = 1.46 around 685 K.</p> </abstract>