Structure and Physical Properties of the Barium Niobium Sulfides BaNbS 3 and BaNb 0.8S 3-δ

• Published in: Journal of solid state chemistry 1995, Vol.115 (2), p.427-434
• Main Authors: Kim, Sung-Jin, Bae, Hyun-Sook, Yee, Kyeong-Ae, Choy, Jin-Ho, Kim, Dong-Kuk, Hur, Nam-Hwi
• Format: Article
• Language: English
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1006/jssc.1995.1155

BaNb 0.8S 3-δ and BaNbS 3 were prepared by heating desired amounts of BaCO 3 and Nb 2O 5 under CS 2/N 2 flow. We found that nominal composition of BaNb 0.8S has sulfur defect, and therefore should be written as BaNb 0.8S 3-δ. XANES experiments of Nb K-edges and XPS experiments proved that the oxidation state of Nb is the same in BaNb 0.8S 3-δ and BaNbS 3. To understand their structures, the electronic and physical properties of the Ba MX 3 ( M = V, Nb, X = S; M = Ta, X = S, Se) phases are compared. In spite of their structural similarity, they exhibit rather different physical properties. It has been known that BaVS 3 is a metal and undergoes a metal to semiconductor transition at 130 K, and this phase shows the ferro antiferromagnetic transition at a lower temperature. However, BaNbS 3 and BaTaS 3 are diamagnetic semiconductors at room temperature. The major factor stabilizing the semiconducting state for BaTa X 3 and BaNbS 3 may be a large spin-orbit coupling rather than a structural distortion.