期刊
ADVANCED FUNCTIONAL MATERIALS
卷 31, 期 52, 页码 -出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adfm.202108006
关键词
brittleness; doping; hardness; mechanical stability; thermoelectrics
类别
资金
- MRSEC program of the National Science Foundation at the Materials Research Center of Northwestern University [DMR-1720139]
- National Aeronautics and Space Administration (NASA) Space Technology Graduate Research Opportunity
- U.S. Department of Commerce, National Institute of Standards and Technology, as part of the Center for Hierarchical Materials Design (CHiMaD) [70NANB19H005]
- DFG (German Science Foundation) [SFB 917]
This study identifies the connections between dislocations, point defects, and brittleness in PbTe materials with various dopants. The results illustrate the consequences of excessive defect engineering and the necessity to consider both mechanical and thermoelectric performance when researching thermoelectric materials for practical applications.
Dislocations and the residual strain they produce are instrumental for the high thermoelectric figure of merit, zT approximate to 2, in lead chalcogenides. However, these materials tend to be brittle, barring them from practical green energy and deep space applications. Nonetheless, the bulk of thermoelectrics research focuses on increasing zT without considering mechanical performance. Optimized thermoelectric materials always involve high point defect concentrations for doping and solid solution alloying. Brittle materials show limited plasticity (dislocation motion), yet clear links between crystallographic defects and embrittlement are hitherto unestablished in PbTe. This study identifies connections between dislocations, point defects, and the brittleness (correlated with Vickers hardness) in single crystal and polycrystalline PbTe with various n- and p-type dopants. Speed of sound measurements show a lack of electronic bond stiffening in p-type PbTe, contrary to the previous speculation. Instead, varied routes of point defect-dislocation interaction restrict dislocation motion and drive embrittlement: dopants with low doping efficiency cause high defect concentrations, interstitial n-type dopants (Ag and Cu) create highly strained obstacles to dislocation motion, and highly mobile dopants can distribute inhomogeneously or segregate to dislocations. These results illustrate the consequences of excessive defect engineering and the necessity to consider both mechanical and thermoelectric performance when researching thermoelectric materials for practical applications.
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