Structural and thermoelectric properties of Pb4In2.6Bi3.4Se13

Quaternary selenide, Pb4In2.6Bi3.4Se13 (x = 2.4 member of the Pb-4(InxBi6-xSe13 solid solution), was synthesized by a solid-state technique, and its structure was determined using powder X-ray diffraction (XRD). Pb4In2.6Bi3.4Se13 crystallizes in the orthorhombic space group Pbam (No. 55) with Z = 4. Lattice parameters and calculated density were determined to be a = 22.152(5) angstrom, b = 27.454(5) angstrom, and c = 4.1354(6) angstrom, V = 2515.0(11) angstrom(3), and D-x = 7.490 g cm(-)(3). The structure consists of Z-shaped ribbon units and corner-shared infinite one-dimensional [InSe4](infinity) chains running parallel to the c-axis. The chains and ribbons are further connected by Pb atoms to form a three-dimensional network. Pb atoms are situated in the center of bicapped trigonal prisms. The compound exhibits a semiconductor feature. The Seebeck coefficient of Pb4In2.6Bi3.4Se13 was found to be -180 mu V K-1 at 295 K and -380 mu V K-1 at 600 K. Combining the values of Seebeck coefficient, electrical conductivity, and thermal conductivity yield a figure of merit, ZT, of about 0.175 at 700 K. The powder XRD pattern of Pb4In2.6Bi3.4Se13 was also determined.