Publication Date

1-29-2020

Department

Ames Laboratory; Chemistry

Campus Units

Ames Laboratory, Chemistry

OSTI ID+

1599454

Report Number

IS-J 10126

DOI

10.1021/jacs.9b12351

Journal Title

Journal of the American Chemical Society

Volume Number

142

Issue Number

4

First Page

2031

Last Page

2041

Abstract

Three novel unconventional clathrates with unprecedented III–V semiconducting frameworks have been synthesized: Cs8In27Sb19, Cs8Ga27Sb19, and Rb8Ga27Sb19. These clathrates represent the first examples of tetrel-free clathrates that are completely composed of main group elements. All title compounds crystallize in an ordered superstructure of clathrate-I in the Ia3̅ space group (No. 206; Z = 8). In the clathrate framework, a full ordering of {Ga or In} and Sb is observed by a combination of high-resolution synchrotron single-crystal and powder X-ray diffraction techniques. Density functional theory (DFT) calculations show that all three clathrates are energetically stable with relaxed lattice constants matching the experimental data. Due to the complexity of the crystal structure composed of heavy elements, the reported clathrates exhibit ultralow thermal conductivities of less than 1 W·m–1·K–1 at room temperature. All compounds are predicted and experimentally confirmed to be narrow-bandgap p-type semiconductors with high Seebeck thermopower values, up to 250 μV·K–1 at 300 K for Cs8In27Sb19. The latter compound shows carrier concentrations and mobilities, 1.42 × 1015 cm–3 and 880 cm2 ·V–1·s–1, which are on par with the values for parent binary InSb, one of the best electronic semiconductors. The high hole carrier mobility is uncommon for complex bulk materials and a highly desirable trait, opening ways to design semiconducting materials based on tunable III–V clathrates.

Language

en

Publisher

Iowa State University Digital Repository, Ames IA (United States)

Available for download on Saturday, January 02, 2021

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