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Hodges JM, Hao S, Grovogui JA, Zhang X, Bailey TP, Li X, Gan Z, Hu YY, Uher C, Dravid VP, Wolverton C, Kanatzidis MG. Chemical Insights into PbSe- x%HgSe: High Power Factor and Improved Thermoelectric Performance by Alloying with Discordant Atoms. J Am Chem Soc 2018; 140:18115-18123. [PMID: 30461275 DOI: 10.1021/jacs.8b11050] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Thermoelectric generators can convert heat directly into usable electric power but suffer from low efficiencies and high costs, which have hindered wide-scale applications. Accordingly, an important goal in the field of thermoelectricity is to develop new high performance materials that are composed of more earth-abundant elements. The best systems for midtemperature power generation rely on heavily doped PbTe, but the Te in these materials is scarce in the Earth's crust. PbSe is emerging as a less expensive alternative to PbTe, although it displays inferior performance due to a considerably smaller power factor S2σ, where S is the Seebeck coefficient and σ is electrical conductivity. Here, we present a new p-type PbSe system, Pb0.98Na0.02Se- x%HgSe, which yields a very high power factor of ∼20 μW·cm-1·K-2 at 963 K when x = 2, a 15% improvement over the best performing PbSe- x%MSe materials. The enhancement is attributed to a combination of high carrier mobility and the early onset of band convergence in the Hg-alloyed samples (∼550 K), which results in a significant increase in the Seebeck coefficient. Interestingly, we find that the Hg2+ cations sit at an off-centered position within the PbSe lattice, and we dub the displaced Hg atoms "discordant". DFT calculations indicate that this feature plays a role in lowering thermal conductivity, and we believe that this insight may inspire new design criteria for engineering high performance thermoelectric materials. The high power factor combined with a decrease in thermal conductivity gives a high figure of merit ZT of 1.7 at 970 K, the highest value reported for p-type PbSe to date.
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Affiliation(s)
- James M Hodges
- Department of Chemistry , Northwestern University , Evanston , Illinois 60208 , United States
| | - Shiqiang Hao
- Department of Materials Science and Engineering , Northwestern University , Evanston , Illinois 60208 , United States
| | - Jann A Grovogui
- Department of Materials Science and Engineering , Northwestern University , Evanston , Illinois 60208 , United States
| | - Xiaomi Zhang
- Department of Materials Science and Engineering , Northwestern University , Evanston , Illinois 60208 , United States
| | - Trevor P Bailey
- Department of Physics , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Xiang Li
- Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32306 , United States
| | - Zhehong Gan
- National High Magnetic Field Laboratory , 1800 East Paul Dirac Drive , Tallahassee , Florida 32310 , United States
| | - Yan-Yan Hu
- Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32306 , United States.,National High Magnetic Field Laboratory , 1800 East Paul Dirac Drive , Tallahassee , Florida 32310 , United States
| | - Ctirad Uher
- Department of Physics , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Vinayak P Dravid
- Department of Materials Science and Engineering , Northwestern University , Evanston , Illinois 60208 , United States
| | - Chris Wolverton
- Department of Materials Science and Engineering , Northwestern University , Evanston , Illinois 60208 , United States
| | - Mercouri G Kanatzidis
- Department of Chemistry , Northwestern University , Evanston , Illinois 60208 , United States
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Chekmeneva E, Díaz-Cruz JM, Ariño C, Esteban M. A novel differential pulse voltammetric method on rotating Au-disk electrode for the study of Hg2+ binding. J Electroanal Chem (Lausanne) 2009. [DOI: 10.1016/j.jelechem.2009.02.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Persson I, Eriksson L, Lindqvist-Reis P, Persson P, Sandström M. An EXAFS Spectroscopic, Large-Angle X-Ray Scattering, and Crystallographic Study of Hexahydrated, Dimethyl Sulfoxide and Pyridine 1-Oxide Hexasolvated Mercury(II) Ions. Chemistry 2008; 14:6687-96. [DOI: 10.1002/chem.200800225] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Nilsson KB, Maliarik M, Persson I, Sandström M. Structure of solvated mercury(II) halides in liquid ammonia, triethyl phosphite and tri-n-butylphosphine solution. Dalton Trans 2008:2303-13. [PMID: 18414756 DOI: 10.1039/b716134d] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Liquid ammonia, trialkyl phosphites, and especially trialkylphosphines, are very powerful electron-pair donor solvents with soft bonding character. The solvent molecules act as strongly coordinating ligands towards mercury(ii), interacting strongly enough to displace halide ligands. In liquid ammonia mercury(ii) chloride solutions separate into two liquid phases; the upper contains tetraamminemercury(ii) complexes, [Hg(NH(3))(4)](2+), and chloride ions in low concentration, while the lower is a dense highly concentrated solution of [Hg(NH(3))(4)](2+) entities, ca. 1.4 mol dm(-3), probably ion-paired by hydrogen bonds to the chloride ions. Mercury(ii) bromide also dissociates to ionic complexes in liquid ammonia and forms a homogeneous solution for which (199)Hg NMR indicates weak bromide association with mercury(ii). When dissolving mercury(ii) iodide in liquid ammonia and triethyl phosphite solvated molecular complexes form in the solutions. The Raman nu(I-Hg-I) symmetric stretching frequency is 132 cm(-1) for the pseudo-tetrahedral [HgI(2)(NH(3))(2)] complex formed in liquid ammonia, corresponding to D(S) = 56 on the donor strength scale. For the Hg(ClO(4))(2)/NH(4)I system in liquid ammonia a (199)Hg NMR study showed [HgI(4)](2-) to be the dominating mercury(ii) complex for mole ratios n(I(-)) : n(Hg(2+)) > or = 6. A large angle X-ray scattering (LAXS) study of mercury(ii) iodide in triethyl phosphite solution showed a [HgI(2)(P(OC(4)H(9))(3))(2)] complex with the Hg-I and Hg-P bond distances 2.750(3) and 2.457(4) A, respectively, in near tetrahedral configuration. Trialkylphosphines generally form very strong bonds to mercury(ii), dissociating all mercury(ii) halides. Mercury(ii) chloride and bromide form solid solvated mercury(ii) halide salts when treated with tri-n-butylphosphine, because of the low permittivity of the solvent. A LAXS study of a melt of mercury(ii) iodide in tri-n-butylphosphine at 330 K resulted in the Hg-I and Hg-P distances 2.851(3) and 2.468(4) A, respectively. The absence of a distinct I-I distance indicates flexible coordination geometry with weak and non-directional mercury(ii) iodide association within the tri-n-butylphosphine solvated complex.
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Affiliation(s)
- Kersti B Nilsson
- Department of Chemistry, Swedish University of Agricultural Sciences, P.O.Box 7015, SE-750 07, Uppsala, Sweden
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