The structure of nano-twinned rhombohedral YCuO_2.66 solved by electron crystallography

In the search for frustrated spin interactions, a YCuO_2.66 phase has been synthesized by a treatment under oxygen pressure of YCuO_2.5. X-ray powder diffraction and electron diffraction studies have been conducted. Electron diffraction shows that the sample is twinned on a 10 nm scale. Precession electron diffraction data obtained from a twinned crystal was treated in order to obtain intensities corresponding to only one of the orientations of the twins. From this data a structure solution was obtained where, as in YCuO_2.5, the Cu atoms form triangular planes. The Cu atoms are linked in two dimensions by oxygen atoms in the present structure whereas in YCuO_2.5 they are only linked in one-dimensional chains.