Synthesis and crystal structure of a new quaternary thioantimonate, Na9Gd5Sb8S26

Abstract

The first Na-containing quaternary rare-earth thioantimonate, Na9Gd5Sb8S26, was synthesized from the reaction of Gd metal, Sb, and S in Na2S flux at 750°C. Black plate-shaped crystals were obtained and their crystal structure was determined by the single-crystal X-ray diffraction method. This compound crystallizes in the orthorhombic space group Pnma (No. 62) with a unit cell of a = 11.406(3) Å, b = 23.765(2) Å, c = 16.923(5) Å, and Z = 4. Na9Gd5Sb8S26 has a complex three-dimensional structure that consists of SbS3, SbS4, GdS6, and GdS7 units. In the structure, three crystallographically different Gd atoms form a staircase-shaped building block, where two Gd atoms share disulfide ions, S2 2-. The formula of the compound can be described as (Na+)9(Gd3+)5(Sb3+) 8(S2-)22(S2 2-) 2. Measurement of the optically diffuse reflectance indicates that Na9Gd5Sb8S26 is a semiconductor with a band gap of 1.63 eV. © 2001 Academic Press.