Journal
ADVANCED FUNCTIONAL MATERIALS
Volume 32, Issue 47, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adfm.202209980
Keywords
band alignments; materials designs; metavalent bonding; solubility limits; thermoelectric
Categories
Funding
- National Natural Science Foundation of China [52071182, 11774347]
- Qinglan Project of the Young and Middle-aged Academic Leader of Jiangsu Province
- Fundamental Research Funds for the Central Universities [30921011107]
- University Synergy Innovation Program of Anhui Province [GXXT-2020-003]
- DFG [SFB 917]
- Excellence Strategy of the Federal Government and the Lander within the ERS RWTH Start-Up grant [StUpPD_392-21]
- Projekt DEAL
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Alloying SnTe with AgSbTe2 significantly enhances the solubility of Ag, leading to improved electronic band structure tuning effects.
SnTe is an emerging Pb-free thermoelectric compound that has drawn significant attention for clean energy conversion. Chemical doping is routinely used to tailor its charge carrier concentration and electronic band structures. However, the efficacy of dopants is often limited by their small solubility. For example, only 0.5% Ag can be incorporated into the SnTe matrix. Yet, significantly more Ag (>7%) can be dissolved if SnTe is alloyed with AgSbTe2. This large enhancement of solubility can be understood from a chemical bonding perspective. Both SnTe and AgSbTe2 employ metavalent bonding as identified by an unusual bond-rupture in atom probe tomography. Density functional theory calculations show that upon Ag doping the energy offset of the upmost two valence bands decreases significantly. This induces band alignment in SnTe, which results in an enhanced power factor over a broad temperature range. Moreover, the increased concentration of point defects and associated lattice strain lead to strong phonon scattering and softening, contributing to an extremely low kappa(L) of 0.30 Wm(-1)K(-1). These synergistic effects contribute to a peak ZT of 1.8 at 873 K and a record-high average ZT of approximate to 1.0 between 400 and 873 K in Sn0.87Mn0.08Sb0.08Te-5%AgSbTe2 alloy.
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