Synthesis and Characterization of New Multinary Selenides A10B18Se37 (A=Sn/Pb; B=In/Sb/Bi)

New multinary selenides with general formula A(10)B(18)Se(37) (A=Sn/Pb; B=In/Sb or Sb/Bi) were synthesized with a new structure type in the monoclinic space group C2/m (No. 12), including Sn10In7Sb11Se37, Sn10Bi18Se37, Sn8.21Pb1.79Bi18Se37, and Sn3.84Pb6.16Sb5.68Bi12.32Se37. The crystal structure is related to Proudite-Felbertalite homologous series and is made up of layered units infinity 2M16Se23 derived from the octahedrally coordinated MSe6 with stepped layers of 16 octahedra overlapped by 8 octahedra units, and 1D ribbons infinity 1M12Se14 with metal centers coordinated by 3 or 5 Se2- anions. Structural anisotropy leads to their layered shape and strong preferred orientation. The quinary selenide Sn3.84Pb6.16Sb5.68Bi12.32Se37 exhibits n-type semiconducting behavior and thermoelectric properties with an optimized thermoelectric figure of merit (zT) reaching similar to 0.09 at 440 K. Density functional theory (DFT) calculation on a charge-balanced model with a triple supercell indicates its indirect band gap.