Superconductivity of a new phase with the hexagonal Nb3S4 type structure: Preparation, crystal structure and electrical properties of nonstoichiometric indium vanadium sulfide

The nonstoichiometric ternary compound In0.69 V6S8 was prepared via a low temperature diffusion reaction between hexagonal V3S4 and In metal. The crystal structure solution reveals that In is strongly disordered within the hexagonal channels of the structure. The analysis of the structural data in connection with the data of other ternary Ax V6S8 phases gives evidences that the V-V bond length within the metal atom zig-zag chains parallel to the crystallographic c-axis is nearly not affected by the valence electron concentration (VEC) per V atom. On the other hand the distance between the chains increases with raising VEC, independent of the nature of the electropositive element A. The electrical resistivity of In0.69 V6S8 was measured between 2 and 300 K. For the first time the authors have observed superconductivity in this compound. The title compound shows a transition into the superconducting state with a transition temperature Tc of 3.7 K