Neutron diffraction studies of $La_4BaCu_4MO_{13+\delta}$ (M = Ni and Co) oxides

The structures of $La_4BaCu_4NiO_{13.20}$ and $La_4BaCu_4CoO_{13.35}$ oxides synthesized in NaOH-KOH flux at 450°C were studied using powder neutron diffraction Rietveld analysis. These oxides crystallize in a tetragonal structure in the P4/m space group with $Ni^{3+}$ or $Co^{3+}$ partially occupying 6-coordinated (1a) and 5-coordinated (4j) sites of the $La_4BaCu_5O_{13+\delta}$ system. Increase in oxygen content with Ni and Co substitution is reflected in the increase in unit-cell volume, compared with that of the parent $La_4BaCu_5O_{13+\delta}$ reserved