Tidying up the mess

doi:10.1126/science.abg0886

GSTDTAP > 气候变化

DOI	10.1126/science.abg0886
	Tidying up the mess
	Yu Liu; Maria Ibáñez
	2021-02-12
发表期刊	Science
出版年	2021
英文摘要	Thermoelectric materials are engines that convert heat into an electrical current. Intuitively, the efficiency of this process depends on how many electrons (charge carriers) can move and how easily they do so, how much energy those moving electrons transport, and how easily the temperature gradient is maintained. In terms of material properties, an excellent thermoelectric material requires a high electrical conductivity σ, a high Seebeck coefficient S (a measure of the induced thermoelectric voltage as a function of temperature gradient), and a low thermal conductivity κ. The challenge is that these three properties are strongly interrelated in a conflicting manner ([ 1 ][1]). On page 722 of this issue, Roychowdhury et al. ([ 2 ][2]) have found a way to partially break these ties in silver antimony telluride (AgSbTe2) with the addition of cadmium (Cd) cations, which increase the ordering in this inherently disordered thermoelectric material. The thermoelectric effect was discovered more than 200 years ago when Volta was conducting experiments with metallic junctions, vessels of water at different temperatures, and dead frogs ([ 3 ][3]). Since then, physicists, chemists, engineers, and material scientists have tried to identify the nature of the effect; understand its microscopic origin; and find, design, and optimize materials with the highest thermoelectric conversion efficiency. The quality of a thermoelectric material is evaluated by using the dimensionless thermoelectric figure of merit, ZT , which includes the relevant properties mentioned above: ZT = σS2 T κ−1, where T is the absolute temperature. Two components contribute to κ: the lattice thermal conductivity κlatt, which represents heat carried by atomic vibrations (phonons), and electronic thermal conductivity κele, which represents heat carried by electrons. As the number of free charge carriers increases, σ and κele also increase, S decreases, and κlatt is unaltered. The optimal charge-carrier concentration for most thermoelectric materials is between 1019 and 1020 carriers per cubic centimeter ([ 4 ][4]). Once the carrier concentration is optimized, further improvements in the ZT require modifying the material electronic structure and its phononic interactions ([ 5 ][5]). In practice, all of these changes are achieved by slightly modifying the compound's chemical composition by using solid solutions or by introducing nanometric secondary phases ([ 6 ][6]). The carrier concentration is commonly tuned by substituting atoms in the crystal structure with other atoms with a different valence. These electronic impurities, or dopants ([ 7 ][7]), change the chemical potential of electrons (the Fermi level) and may also affect the material's electronic structure. The energy-band structure is linked with the overlapping of atomic orbitals and properties such as the ionization energy, bond energy, and bond length. Thus, the choice of an adequate substitutional atom to modify the electronic band becomes less intuitive ([ 6 ][6]). Introducing atomic defects in the host lattice will also directly affect κ by adding disorder and local strain, which alters the lattice vibrations. Last, given that all of the above is optimized, κ can be further reduced by introducing nano- or microscale features (ideally transparent to electrons) that act as barriers for the propagation of phonons ([ 8 ][8]). Usually, to maximize ZT in a given material, all the above strategies should be cumulatively integrated. In the well-studied material lead telluride (PbTe) ([ 9 ][9]), the optimal number of free carriers is obtained by replacing a small percentage of the double-charged Pb atoms with a single-charged cation. Proper doping with Na creates a p-type material, Pb0.98Na0.02Te, which has a carrier concentration of around 1020 carriers per cubic centimeter. A solid solution of PbTe with SrTe increases the bandgap and shifts the light and heavy bands closer to each other. Such band conversion increases S . Last, secondary SrTe phases are formed in the PbTe matrix material by pushing the content of Sr beyond the solubility limit, which reduces κlatt. ![Figure][10] Thermoelectricity comes to order Roychowdhury et al. improved the thermoelectric performance of silver antimony telluride (AgSbTe2) by partially substituting antimony (Sb) atoms with cadmium (Cd). GRAPHIC: A. KITTERMAN/ SCIENCE In short, to maximize ZT for PbTe, it was necessary to introduce lattice imperfections (Na and Sr at the Pb sites) and nanoprecipitates (SrTe)—that is, increase material structural disorder. Roychowdhury et al. embraced the challenge of optimizing the thermoelectric performance of an already highly disordered material, AgSbTe2, a complex material system that can exhibit different structural properties depending on the synthetic conditions ([ 10 ][11]). In line with previous reports, Roychowdhury et al. showed that polycrystalline AgSbTe2 is inherently disordered because of the random distribution of Ag and Sb over the cubic structure's cationic sites (see the figure) and appearance of Ag2Te secondary phase ([ 11 ][12], [ 12 ][13]). To modify material properties, they replace Sb3+ atoms with Cd2+. Such elemental substitution has further consequences than the simple increase of free charge carriers. Theoretical calculations showed that Cd preferentially occupies disordered Sb sites, which lowered ordered cationic configurations' formation energy and favored their presence. Although the disordered phase is cubic, the ordered counterpart can be formed either in a cubic or rhombohedral crystal structure with different cationic configurations at a similar energy cost, which results in Cd-doped AgSbTe2 having different ordered nanoscale domains (see the figure). The strain between the two lattice configuration results in nanoscale superstructures (strain ripples). The promoted changes in the atomic arrangement directly translate into an enhanced σ and reduced κ. Roychowdhury et al. explained that the increase in σ is associated with the increase of carriers and the reduction of disorder-induced fluctuations in the lattice potential, which facilitate carrier movement through the material. Two main factors hinder heat transport in this Cd-doped higher-order configuration: The nanoscale domain ripples as well as the local strain around Cd sites. Overall, Cd's multifaceted role allowed the authors to achieve a ZT of up to 1.5 at room temperature, a maximum ZT of 2.6 at 573 K, and an average ZT of 1.8. These values are among the highest reported to date. The idiosyncrasy of the strategy presented by Roychowdhury et al. is that the introduction of a foreign atom into the crystal lattice yields a material with a higher ordered state. Considering that most thermoelectric materials are optimized through added disorder (as in the archetypal PbTe case), this result suggests a new avenue for thermoelectric material design through the optimization of atomic ordering. 1. [↵][14]1. A. Zevalkink et al ., Appl. Phys. Rev. 5, 021303 (2018). [OpenUrl][15] 2. [↵][16]1. S. Roychowdhury et al ., Science 371, 722 (2021). [OpenUrl][17][Abstract/FREE Full Text][18] 3. [↵][19]1. D. Beretta et al ., Mater. Sci. Eng. Rep. 138, 100501 (2019). [OpenUrl][20] 4. [↵][21]1. G. J. Snyder, 2. E. S. Toberer , Nat. Mater. 7, 105 (2008). [OpenUrl][22][CrossRef][23][PubMed][24][Web of Science][25] 5. [↵][26]1. L.-D. Zhao, 2. V. P. Dravid, 3. M. G. Kanatzidis , Energy Environ. Sci. 7, 251 (2014). [OpenUrl][27][CrossRef][28] 6. [↵][29]1. W. G. Zeier et al ., Angew. Chem. Int. Ed. 55, 6826 (2016). [OpenUrl][30][CrossRef][31][PubMed][32] 7. [↵][33]1. M. Ibáñez et al ., Chem. Mater. 29, 7093 (2017). [OpenUrl][34] 8. [↵][35]1. K. Biswas et al ., Nature 489, 414 (2012). [OpenUrl][36][CrossRef][37][PubMed][38][Web of Science][39] 9. [↵][40]1. G. Tan et al ., Nat. Commun. 7, 12167 (2016). [OpenUrl][41] 10. [↵][42]1. S. V. Barabash, 2. V. Ozolins, 3. C. Wolverton , Phys. Rev. Lett. 101, 155704 (2008). [OpenUrl][43][CrossRef][44][PubMed][45] 11. [↵][46]1. K. T. Wojciechowski, 2. M. Schmidt , Phys. Rev. B Condens. Matter Mater. Phys. 79, 184202 (2009). [OpenUrl][47] 12. [↵][48]1. R. W. Armstrong, 2. J. W. Faust Jr., 3. W. A. Tiller , J. Appl. Phys. 31, 1954 (1960). [OpenUrl][49][CrossRef][50] [1]: #ref-1 [2]: #ref-2 [3]: #ref-3 [4]: #ref-4 [5]: #ref-5 [6]: #ref-6 [7]: #ref-7 [8]: #ref-8 [9]: #ref-9 [10]: pending:yes [11]: #ref-10 [12]: #ref-11 [13]: #ref-12 [14]: #xref-ref-1-1 "View reference 1 in text" [15]: {openurl}?query=rft.jtitle%253DAppl.%2BPhys.%2BRev.%26rft.volume%253D5%26rft.spage%253D021303%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [16]: #xref-ref-2-1 "View reference 2 in text" [17]: {openurl}?query=rft.jtitle%253DScience%26rft.stitle%253DScience%26rft.aulast%253DRoychowdhury%26rft.auinit1%253DS.%26rft.volume%253D371%26rft.issue%253D6530%26rft.spage%253D722%26rft.epage%253D727%26rft.atitle%253DEnhanced%2Batomic%2Bordering%2Bleads%2Bto%2Bhigh%2Bthermoelectric%2Bperformance%2Bin%2BAgSbTe2%26rft_id%253Dinfo%253Adoi%252F10.1126%252Fscience.abb3517%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [18]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Mzoic2NpIjtzOjU6InJlc2lkIjtzOjEyOiIzNzEvNjUzMC83MjIiO3M6NDoiYXRvbSI7czoyMjoiL3NjaS8zNzEvNjUzMC82NzguYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9 [19]: #xref-ref-3-1 "View reference 3 in text" [20]: {openurl}?query=rft.jtitle%253DMater.%2BSci.%2BEng.%2BRep.%26rft.volume%253D138%26rft.spage%253D100501%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [21]: #xref-ref-4-1 "View reference 4 in text" [22]: {openurl}?query=rft.jtitle%253DNature%2Bmaterials%26rft.stitle%253DNat%2BMater%26rft.aulast%253DSnyder%26rft.auinit1%253DG.%2BJ.%26rft.volume%253D7%26rft.issue%253D2%26rft.spage%253D105%26rft.epage%253D114%26rft.atitle%253DComplex%2Bthermoelectric%2Bmaterials.%26rft_id%253Dinfo%253Adoi%252F10.1038%252Fnmat2090%26rft_id%253Dinfo%253Apmid%252F18219332%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [23]: /lookup/external-ref?access_num=10.1038/nmat2090&link_type=DOI [24]: /lookup/external-ref?access_num=18219332&link_type=MED&atom=%2Fsci%2F371%2F6530%2F678.atom [25]: /lookup/external-ref?access_num=000252673000014&link_type=ISI [26]: #xref-ref-5-1 "View reference 5 in text" [27]: {openurl}?query=rft.jtitle%253DEnergy%2BEnviron.%2BSci.%26rft.volume%253D7%26rft.spage%253D251%26rft_id%253Dinfo%253Adoi%252F10.1039%252FC3EE43099E%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [28]: /lookup/external-ref?access_num=10.1039/C3EE43099E&link_type=DOI [29]: #xref-ref-6-1 "View reference 6 in text" [30]: {openurl}?query=rft.jtitle%253DAngew.%2BChem.%2BInt.%2BEd.%26rft.volume%253D55%26rft.spage%253D6826%26rft_id%253Dinfo%253Adoi%252F10.1002%252Fanie.201508381%26rft_id%253Dinfo%253Apmid%252F27111867%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [31]: /lookup/external-ref?access_num=10.1002/anie.201508381&link_type=DOI [32]: /lookup/external-ref?access_num=27111867&link_type=MED&atom=%2Fsci%2F371%2F6530%2F678.atom [33]: #xref-ref-7-1 "View reference 7 in text" [34]: {openurl}?query=rft.jtitle%253DChem.%2BMater.%26rft.volume%253D29%26rft.spage%253D7093%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [35]: #xref-ref-8-1 "View reference 8 in text" [36]: {openurl}?query=rft.jtitle%253DNature%26rft.stitle%253DNature%26rft.aulast%253DBiswas%26rft.auinit1%253DK.%26rft.volume%253D489%26rft.issue%253D7416%26rft.spage%253D414%26rft.epage%253D418%26rft.atitle%253DHigh-performance%2Bbulk%2Bthermoelectrics%2Bwith%2Ball-scale%2Bhierarchical%2Barchitectures.%26rft_id%253Dinfo%253Adoi%252F10.1038%252Fnature11439%26rft_id%253Dinfo%253Apmid%252F22996556%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [37]: /lookup/external-ref?access_num=10.1038/nature11439&link_type=DOI [38]: /lookup/external-ref?access_num=22996556&link_type=MED&atom=%2Fsci%2F371%2F6530%2F678.atom [39]: /lookup/external-ref?access_num=000308860900041&link_type=ISI [40]: #xref-ref-9-1 "View reference 9 in text" [41]: {openurl}?query=rft.jtitle%253DNat.%2BCommun.%26rft.volume%253D7%26rft.spage%253D12167%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [42]: #xref-ref-10-1 "View reference 10 in text" [43]: {openurl}?query=rft.jtitle%253DPhysical%2BReview%2BLetters%26rft.stitle%253DPhysical%2BReview%2BLetters%26rft.aulast%253DBarabash%26rft.auinit1%253DS.%2BV.%26rft.volume%253D101%26rft.issue%253D15%26rft.spage%253D155704%26rft.epage%253D155704%26rft.atitle%253DFirst-principles%2Btheory%2Bof%2Bcompeting%2Border%2Btypes%252C%2Bphase%2Bseparation%252C%2Band%2Bphonon%2Bspectra%2Bin%2Bthermoelectric%2BAgPbmSbTe%2528m%252B2%2529%2Balloys.%26rft_id%253Dinfo%253Adoi%252F10.1103%252FPhysRevLett.101.155704%26rft_id%253Dinfo%253Apmid%252F18999614%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [44]: /lookup/external-ref?access_num=10.1103/PhysRevLett.101.155704&link_type=DOI [45]: /lookup/external-ref?access_num=18999614&link_type=MED&atom=%2Fsci%2F371%2F6530%2F678.atom [46]: #xref-ref-11-1 "View reference 11 in text" [47]: {openurl}?query=rft.jtitle%253DPhys.%2BRev.%2BB%2BCondens.%2BMatter%2BMater.%2BPhys.%26rft.volume%253D79%26rft.spage%253D184202%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [48]: #xref-ref-12-1 "View reference 12 in text" [49]: {openurl}?query=rft.jtitle%253DJ.%2BAppl.%2BPhys.%26rft.volume%253D31%26rft.spage%253D1954%26rft_id%253Dinfo%253Adoi%252F10.1063%252F1.1735478%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [50]: /lookup/external-ref?access_num=10.1063/1.1735478&link_type=DOI
领域	气候变化 ; 资源环境
URL	查看原文
引用统计
文献类型	期刊论文
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/314076
专题	气候变化资源环境科学
推荐引用方式 GB/T 7714	Yu Liu,Maria Ibáñez. Tidying up the mess[J]. Science,2021.
APA	Yu Liu,&Maria Ibáñez.(2021).Tidying up the mess.Science.
MLA	Yu Liu,et al."Tidying up the mess".Science (2021).