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Title: Natural off-stoichiometry causes carrier doping in half-Heusler filled tetrahedral structures

Authors:
; ;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1342611
Grant/Contract Number:
FG02-13ER46959; AC02-05CH11231
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 95; Journal Issue: 8; Related Information: CHORUS Timestamp: 2017-02-06 11:58:56; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society
Country of Publication:
United States
Language:
English

Citation Formats

Yu, Yonggang G., Zhang, Xiuwen, and Zunger, Alex. Natural off-stoichiometry causes carrier doping in half-Heusler filled tetrahedral structures. United States: N. p., 2017. Web. doi:10.1103/PhysRevB.95.085201.
Yu, Yonggang G., Zhang, Xiuwen, & Zunger, Alex. Natural off-stoichiometry causes carrier doping in half-Heusler filled tetrahedral structures. United States. doi:10.1103/PhysRevB.95.085201.
Yu, Yonggang G., Zhang, Xiuwen, and Zunger, Alex. Fri . "Natural off-stoichiometry causes carrier doping in half-Heusler filled tetrahedral structures". United States. doi:10.1103/PhysRevB.95.085201.
@article{osti_1342611,
title = {Natural off-stoichiometry causes carrier doping in half-Heusler filled tetrahedral structures},
author = {Yu, Yonggang G. and Zhang, Xiuwen and Zunger, Alex},
abstractNote = {},
doi = {10.1103/PhysRevB.95.085201},
journal = {Physical Review B},
number = 8,
volume = 95,
place = {United States},
year = {Fri Feb 03 00:00:00 EST 2017},
month = {Fri Feb 03 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1103/PhysRevB.95.085201

Citation Metrics:
Cited by: 6works
Citation information provided by
Web of Science

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  • Electronic structure theory has recently been used to propose hypothetical compounds in presumed crystal structures, seeking new useful functional materials. In some cases, such hypothetical materials are metastable, albeit with technologically useful long lifetimes. Yet, in other cases, suggested hypothetical compounds may be significantly higher in energy than their lowest-energy crystal structures or competing phases, making their synthesis and eventual device-stability questionable. By way of example, the focus here is on the family of 1:1:1 compounds ABX called 'filled tetrahedral structure' (sometimes called Half-Heusler) in the four groups with octet electron count: I-I-VI (e.g., CuAgSe), I-II-V (e.g., AgMgAs), I-III-IV (e.g.,more » LiAlSi), and II-II-IV (e.g., CaZnSn). First-principles thermodynamics is used to sort the lowest-energy structure and the thermodynamic stability of the 488 unreported hypothetical ABX compounds, many of which were previously proposed to be useful technologically. It is found that as many as 235 of the 488 are unstable with respect to decomposition (hence, are unlikely to be viable technologically), whereas other 235 of the unreported compounds are predicted to be thermodynamically stable (hence, potentially interesting new materials). 18 additional materials are too close to determine. The electronic structures of these predicted stable compounds are evaluated, seeking potential new material functionalities.« less
  • We report on the effect of off-stoichiometry on the temperature dependence of electrical resistivity, the Seebeck coefficient, and the Hall coefficient in the Heusler-type Fe{sub 2}VAl compound. While the stoichiometric Fe{sub 2}VAl exhibits a semiconductorlike resistivity behavior, a small deviation of the Al content from stoichiometry causes a significant decrease in the low-temperature resistivity and a large enhancement in the Seebeck coefficient. Substantial enhancements for the Seebeck coefficient are in reasonable accord with changes in the Hall coefficient and can be explained on the basis of the electronic structure, where the Fermi level shifts slightly from the center of amore » pseudogap due to off stoichiometry.« less
  • The thermoelectric properties of Heusler-type Fe{sub 2−x}V{sub 1+x}Al{sub 1−y}Si{sub y} and Fe{sub 2−x}V{sub 1+x−y}Ti{sub y}Al alloys have been investigated to clarify which off-stoichiometric alloy, i.e., V-rich (x > 0) or V-poor (x < 0), is more effective in enhancing the Seebeck coefficient when doped by Si and Ti, while retaining a low electrical resistivity. Large Seebeck coefficients of −182 μV/K and 110 μV/K at 300 K are obtained for n-type Fe{sub 1.95}V{sub 1.05}Al{sub 0.97}Si{sub 0.03} and p-type Fe{sub 2.04}V{sub 0.93}Ti{sub 0.03}Al, respectively. When the Seebeck coefficient is plotted as a function of valence electron concentration (VEC), the VEC dependence for the doped off-stoichiometric alloys falls on characteristicmore » curves depending on the off-stoichiometric composition x. It is concluded that a larger Seebeck coefficient with a negative sign can be obtained for the V-rich alloys rather than the V-poor alloys, whilst good p-type materials are always derived from the V-poor alloys. Substantial enhancements in the Seebeck coefficient for the off-stoichiometric alloys could be achieved by a favorable modification in the electronic structure around the Fermi level through the antisite V or Fe defect formation.« less