Journal
MATERIALS TODAY ADVANCES
Volume 7, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.mtadv.2020.100094
Keywords
Bismuthides; Crystal structure; Single-crystal X-ray diffraction; New material synthesis; Narrow-gap semiconductor
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Funding
- U.S. Department of Energy [DE-SC0008885]
- U.S. Department of Energy (DOE) [DE-SC0008885] Funding Source: U.S. Department of Energy (DOE)
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The Zintl phase Ca14AlBi11 has been synthesized and structurally characterized for the first time. Its crystal structure has been carefully determined by single-crystal X-ray diffraction methods, and shown to crystallize in the tetragonal space group I4(1)/acd, No. 142 (Z = 8). Not surprisingly, Ca14AlBi11 adopts the Ca14AlSb11-structure type, although Ca14AlBi11 is the first alumo-bismuthide among the '14-1-11' family whose structure is unequivocally established. In the respective Ca-Al-Bi ternary system, so far, Ca14AlBi11 is only the second identified phase. Electronic structure calculations for this new bismuthide indicate the opening of a small gap at the Fermi level, suggestive of intrinsic semiconducting behavior. Resistivity measurements on as-synthesized single crystalline sample show temperature dependence akin to those of heavily doped semiconductors or the bad metals. In addition to the moderately high electrical conductivity (rho(300) = 1.05 m Omega cm), specimens of Ca14AlBi11 also exhibit excellent thermopower, with high-temperature (HT) values of the Seebeck coefficient approaching and possibly exceeding 200 mu V/K. These metrics, coupled with preliminary HT conductivity estimates, are comparable with the best state-of-the-art p-type Zintl thermoelectric materials and are among the best within the known bismuthides with the same atomic arrangements. Therefore, Ca14AlBi11 represents a new platform for the development of a novel, low-cost thermoelectric materials family with first-class transport properties and enhanced thermal stability. Initial data suggest that Ca14AlBi11 is amenable to doping, which opens up many opportunities for tuning charge-carrier concentration and optimizing the transport properties in this new, HT thermoelectric material. (C) 2020 The Author(s). Published by Elsevier Ltd.
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