POWDER X-RAY AND IR STUDIES OF THE NEW OXYSELENIDES MOCUSE (M=BI, GD, DY)

The group of oxyselenides with the formula (MO)(CuSe) (M = Gd, Dy, and Ho) has been prepared by reacting M(2)O(3), Cu, M, and Se at 750 degrees C for 240 hr. All compounds were characterized by IR-spectra analysis. Powder diffraction structure analysis was made for GdOCuSe and DyOCuSe (Rietveld profile analysis) in P4/nmm symmetry. Crystal data are as follows: GdOCuSe, a = 3.9186(2), c = 8.723(5) ii; DyOCuSe, a = 3.8854(2), c 8.701(4) Angstrom; HoOCuSe,a = 3.866(2), c = 8.685(7) Angstrom. Crystal structures are built up of [M(2)O(2)] fluorite-like layers (M = Gd, Dy), normal to the Z-axis, alternating with [Cu2Se2] layers formed by slightly distorted edge-sharing CuSe4 tetrahedra. The structures were compared with those of other similar layered compounds. (C) 1995 Academic Press, Inc.