Preparation and crystal structure analysis of CeCuOS

A single phase of CeCuOS was prepared by sulfurization of starting materials, CeO2 + Cu2S, and subsequent post-annealing in evacuated silica tubes. The crystal structure of the CeCuOS single phase was examined by the Rietveld analysis. The shrinkage of the unit-cell volume for CeCuOS was obviously observed in the series of LnCuOS (Ln = La-Nd) oxysulfides. The examination of interatomic distances revealed that Ce-S distances in CeCuOS are shorter than those predicted from the lanthanide contraction and this short Ce-S bond length is responsible for the unit-cell-volume shrinkage of CeCuOS. The origin of the shrinkage is discussed in the viewpoints of the Ce valence and interatomic distances along with the results of magnetic measurements. (C) 2002 Elsevier Science (USA). All rights reserved.