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 M₂O ₃, Cu, M, and Se at 750°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) Å; DyOCuSe, a = 3.8854(2), c = 8.701(4) Å; HoOCuSe, a = 3.866(2), c = 8.685(7) Å. Crystal structures are built up of [ M₂O ₂] fluorite-like layers ( M = Gd, Dy), normal to the Z-axis, alternating with [Cu 2Se 2] layers formed by slightly distorted edge-sharing CuSe ⁴ tetrahedra. The structures were compared with those of other similar layered compounds.