Superconductivity in BiOSCl with Bi-Cl Planar Layers.

A quaternary compound BiOSCl, which consists of novel [BiSCl] layers, is reported. It adopts a layered structure of the space group I4/ mmm (No. 139) with lattice parameters: a = 3.927(1) Å, c = 21.720(5) Å. In this compound, bismuth and chlorine atoms form an infinite planar layer, which is unique among the bismuth halides. Superconductivity is observed in both polycrystals and single crystals, and is significantly enhanced in the samples prepared with less sulfur or at higher temperatures. By tuning the content of sulfur, BiOSCl can be converted from a semiconductor into a superconductor. The superconducting critical temperature ranges from 2.6 to 3.5 K. Our discovery of the [BiSCl] layer opens another door in searching for the bismuth compounds with novel physical properties.