Crystal Structure Refinement of the Oxygen-rich RCuO2+δ(R=Y and La) Delafossite by Neutron Diffraction

We have refined the structural parameters of delafossite-type cuprates, i. e. (Y0. 95Ca0.05)CuO2. 02 and LaCuO2.02 as well as the derived phases containing excess oxygen, i. e. (Y0. 95Ca0.05)CuO2. 49 and LaCuO2.64 from powder neutron diffraction data at room temperature. According to Rietveld analyses, (Y0.95Ca0.05)CuO2.02 and LaCuO2.20 delafossites could be analyzed with space groups of P63/mmc and R3m, respectively. The metal- and oxygen-atom lattices were perfectly stoichiometric and there was no major stacking faults in the phases. For (Y0.95Ca0.05)CuO2. 49’ the structure was refined in the P63/m space groups with sufficient R-factors, as previously proposed by Sora et al. The excess oxygen atoms are likely located in the distorted triangular Cu plane.