Chemistry - A European Journal
Chemistry - A European Journal
5 years ago

Ultrahigh Average Thermoelectric Figure of Merit, Low Lattice Thermal Conductivity and Enhanced Microhardness in Nanostructured (GeTe)x(AgSbSe2)100−x

Ultrahigh Average Thermoelectric Figure of Merit, Low Lattice Thermal Conductivity and Enhanced Microhardness in Nanostructured (GeTe)x(AgSbSe2)100−x
Suresh Perumal, Subhajit Roychowdhury, Jay Ghatak, Manisha Samanta, Kanishka Biswas
Waste heat sources are generally diffused and provide a range of temperatures rather than a particular temperature. Thus, thermoelectric waste heat to electricity conversion requires a high average thermoelectric figure of merit (ZTavg) of materials over the entire working temperature along with a high peak thermoelectric figure of merit (ZTmax). Herein an ultrahigh ZTavg of 1.4 for (GeTe)80(AgSbSe2)20 [TAGSSe-80, T=tellurium, A=antimony, G=germanium, S=silver, Se=selenium] is reported in the temperature range of 300–700 K, which is one of the highest values measured amongst the state-of-the-art Pb-free polycrystalline thermoelectric materials. Moreover, TAGSSe-80 exhibits a high ZTmax of 1.9 at 660 K, which is reversible and reproducible with respect to several heating–cooling cycles. The high thermoelectric performance of TAGSSe-x is attributed to extremely low lattice thermal conductivity (κlat), which mainly arises due to extensive phonon scattering by hierarchical nano/meso-structures in the TAGSSe-x matrix. Addition of AgSbSe2 in GeTe results in κlat of ≈0.4 W mK−1 in the 300–700 K range, approaching to the theoretical minimum limit of lattice thermal conductivity (κmin) of GeTe. Additionally, (GeTe)80(AgSbSe2)20 exhibits a higher Vickers microhardness (mechanical stability) value of ≈209 kgf mm−2 compared to the other state-of-the-art metal chalcogenides, making it an important material for thermoelectrics. Merit badge: Thermoelectric waste heat to electricity conversion requires a high average thermoelectric figure of merit (ZTavg) over the entire working temperature range. (GeTe)80(AgSbSe2)20 (TAGSSe-80), a Pb-free polycrystalline bulk sample, exhibits an ultrahigh ZTavg of 1.4 due to extremely low lattice thermal conductivity in the 300–700 K range.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201701480

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