Single crystal structure and electrical properties of Cu8Ni4Sn12S32

Starting from pure metals and sulphur in evacuated silica tubes single crys tals of Cu8Ni4Sn12S32 have been obtained by heating at 750 degreesC. It cry stallizes in the Fd (3) over barm space group with Z = 1 and a = 10.3022 (6 ) Angstrom. The atomic parameters and anisotropic thermal parameters were r efined to give a final R value of 0.0157. The mode of filling of tetrahedra l and octahedral cavities of the anionic close packing has been analyzed ta king their sizes into account. The difference in space groups for the analo gous Fe and Cd thiospinels (I4(1)/a) compared to that of the title compound (Fd (3) over barm) appears to be due to the larger size of the Fe2+ (HS) a nd Cd2+ ions leading to distorted octahedra. Cu8Ni4Sn12S32 shows semiconduc ting behavior with resistivity of 10(2) Omega -cm at room temperature with a small band gap (similar to0.05 eV). (C) 2001 Elsevier Science B.V. All ri ghts reserved.