The new ternary bismuth sulfide KBi3S5 forms from the reaction of Bi in a K2Sx flux at 300 °C (94% yield). The compound crystallizes in the orthorhombic space group Pnma (no. 62) with a = 17.013(5) Å, b = 4.076(2) Å, c = 17.365(4) Å, V = 1204(2) Å3, and Z = 4 (final R/Rw = 5.1/6.7%), data with Fo2 > 3σ(Fo2) 782, no. of variables 59, 2θmax = 50°. The compound contains an open framework composed of edge-sharing BiS6 octahedra to form large tunnels which are occupied by K+ ions fractionally distributed over two sites. The S•••S distances across the channel range from 9.45-14.02 A. KBi3S5 is a semiconductor with a band-gap of 1.21 eV. It undergoes a structural change upon heating at 520 °C. KBi3S5 exhibits topotactic ion-exchange with RbCl to give β-RbBi3S5 at 350—380 °C. Ion-exchange with aqueous HC1 in air forms an oxidized, metastable bismuth sulfide which undergoes endothermic decomposition to Bi2S3 at ~140 °C.
ASJC Scopus subject areas
- Colloid and Surface Chemistry