Crystal structure and physical properties of the quaternary manganese-bearing pavonite homologue Mn1.34Sn6.66Bi8Se20

The quaternary manganese tin bismuth selenide, Mn1.34Sn6.66Bi8Se20 was synthesized by combining constituent elements at 723 K. Single crystal structure determination revealed that Mn1.34Sn6.66Bi8Se20 is isostructural to the mineral pavonite, AgBi3S5, crystallizing in the monoclinic space group C2/m (#12) with a=13.648(3) Å; b=4.175(1) Å; c=17.463(4) Å; β=93.42(3)°. In the structure, two kinds of layered modules, denoted A and B, alternate along [0 0 1]. Module A consists of paired chains of face-sharing monocapped trigonal prisms (around Bi/Sn) separated by a single chain of edge-sharing octahedra (around Mn/Sn). Module B represents a NaCl-type fragment of edge-sharing [(Bi/Sn)Se6] octahedra. Mn1.34Sn6.66Bi8Se20 is an n-type narrow gap semiconductor with Eg∼0.29 eV. At 300 K, thermopower, electrical conductivity and lattice thermal conductivity values are −123 μV/K, 47 S/cm and 0.6 W/m K, respectively. Mn1.34Sn6.66Bi8Se20 is paramagnetic at high temperatures and undergoes antiferromagnetic transition at TN=10 K.