Sj. Kim et al., STRUCTURE AND PHYSICAL-PROPERTIES OF THE BARIUM NIOBIUM SULFIDES BANBS3 AND BANB0.8S3-DELTA, Journal of solid state chemistry, 115(2), 1995, pp. 427-434
BaNb0.8S3-delta and BaNbS3 were prepared by heating desired amounts of
BaCo3 and Nb2O5 under CS2/N-2 flow. We found that nominal composition
of BaNb0.8S has sulfur defect, and therefore should be written as BaN
b0.8S3-delta XANES experiments of Nb K-edges and XPS experiments prove
d that the oxidation state of Nb is the same in BaNb0.8S3-delta and Ba
NbS3. To understand their structures, the electronic and physical prop
erties of the BaMX(3) (M = V, Nb, X = S; M = Ta, X = S, Se) phases are
compared. In spite of their structural similarity, they exhibit rathe
r different physical properties. It has been known that BaVS3 is a met
al and undergoes a metal to semiconductor transition at 130 K, and thi
s phase shows the ferro antiferromagnetic transition at a lower temper
ature. However, BaNbS3 and BaTaS3 are diamagnetic semiconductors at ro
om temperature. The major factor stabilizing the semiconducting state
for BaTaX(3) and BaNbS3 may be a large spin-orbit coupling rather than
a structural distortion. (C) 1995 Academic Press, Inc.