title: Pb7Bi4Se13: a lillianite homologue with promising thermoelectric properties.
abstract: Pb(7)Bi(4)Se(13) crystallizes in the monoclinic space group C2/m (No. 12) with a = 13.991(3) Å, b = 4.262(2) Å, c = 23.432(5) Å, and β = 98.3(3)° at 300 K. In its three-dimensional structure, two NaCl-type layers A and B with respective thicknesses N(1) = 5 and N(2) = 4 [N = number of edge-sharing (Pb/Bi)Se6 octahedra along the central diagonal] are arranged along the c axis in such a way that the bridging monocapped trigonal prisms, PbSe7, are located on a pseudomirror plane parallel to (001). This complex atomic-scale structure results in a remarkably low thermal conductivity (∼0.33 W m(-1) K(-1) at 300 K). Electronic structure calculations and diffuse-reflectance measurements indicate that Pb(7)Bi(4)Se(13) is a narrow-gap semiconductor with an indirect band gap of 0.23 eV. Multiple peaks and valleys were observed near the band edges, suggesting that Pb(7)Bi(4)Se(13) is a promising compound for both n- and p-type doping. Electronic-transport data on the as-grown material reveal an n-type degenerate semiconducting behavior with a large thermopower (∼-160 μV K(-1) at 300 K) and a relatively low electrical resistivity. The inherently low thermal conductivity of Pb(7)Bi(4)Se(13) and its tunable electronic properties point to a high thermoelectric figure of merit for properly optimized samples.
authors.affiliation: Department of Materials Science and Engineering and §Department of Physics, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Alan
authors.initials: A
authors.lastname: Olvera
authors.forename: Guangsha
authors.initials: G
authors.lastname: Shi
authors.forename: Honore
authors.initials: H
authors.lastname: Djieutedjeu
authors.forename: Alexander
authors.initials: A
authors.lastname: Page
authors.forename: Ctirad
authors.initials: C
authors.lastname: Uher
authors.forename: Emmanouil
authors.initials: E
authors.lastname: Kioupakis
authors.forename: Pierre F P
authors.initials: PF
authors.lastname: Poudeu