Crystal Structure and Physical Properties of Fe_1.5Pb_5.5In₁₀S₂₂

A new compound, Fe2+1.5Pb2+5.5In3+10S2-22, was found in the Fe−Pb−In−S system. The crystals had a shiny metallic gray luster and were obtained in a barlike shape. The melting and recrystallizing points are 1098 and 1090 K, respectively. The crystal structure determined by X-ray diffraction is P2/m, a = 14.558(1) Å, b = 3.8556(3) Å, c = 15.558(1) Å, β = 96.876(1)°, V = 867.0(1) Å3, Z = 1, Dc = 5.893 g/cm3, and R1 = 3.78%, which is an isostructure with Sn5.5In11S22. In the structure, lead atoms exist at three crystallographically independent sites, and one of them, Pb1, is occupied by a quarter of indium atoms. All of the Fe ions are randomly distributed at six indium sites. This compound is a semiconductor with a band gap, Ea = 0.95 eV. The dominant magnetic interaction is antiferromagnetic, but magnetic orderings are not observed down to 2 K.