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Highly Converged Valence Bands and Ultralow Lattice Thermal Conductivity for High‐Performance SnTe Thermoelectrics
Author(s) -
Sarkar Debattam,
Ghosh Tanmoy,
Banik Ananya,
Roychowdhury Subhajit,
Sanyal Dirtha,
Biswas Kanishka
Publication year - 2020
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202003946
Subject(s) - thermoelectric effect , seebeck coefficient , doping , figure of merit , materials science , thermoelectric materials , phonon , electrical resistivity and conductivity , valence (chemistry) , band gap , thermal conductivity , condensed matter physics , analytical chemistry (journal) , chemistry , optoelectronics , thermodynamics , physics , organic chemistry , chromatography , quantum mechanics , composite material
Abstract A two‐step optimization strategy is used to improve the thermoelectric performance of SnTe via modulating the electronic structure and phonon transport. The electrical transport of self‐compensated SnTe (that is, Sn 1.03 Te) was first optimized by Ag doping, which resulted in an optimized carrier concentration. Subsequently, Mn doping in Sn 1.03− x Ag x Te resulted in highly converged valence bands, which improved the Seebeck coefficient. The energy gap between the light and heavy hole bands, i.e. Δ E v decreases to 0.10 eV in Sn 0.83 Ag 0.03 Mn 0.17 Te compared to the value of 0.35 eV in pristine SnTe. As a result, a high power factor of ca. 24.8 μW cm −1 K −2 at 816 K in Sn 0.83 Ag 0.03 Mn 0.17 Te was attained. The lattice thermal conductivity of Sn 0.83 Ag 0.03 Mn 0.17 Te reached to an ultralow value (ca. 0.3 W m −1 K −1 ) at 865 K, owing to the formation of Ag 7 Te 4 nanoprecipitates in SnTe matrix. A high thermoelectric figure of merit ( z T ≈1.45 at 865 K) was obtained in Sn 0.83 Ag 0.03 Mn 0.17 Te.