Neutron diffraction studies of La<SUB>4</SUB>BaCu<SUB>4</SUB>MO<SUB>13+&#948;</SUB> (M = Ni and Co) oxides

The structures of La4BaCu4NiO13.20 and La4BaCu4CoO13.35 oxides synthesized in NaOH-KOH flux at 450&#176;C were studied using powder neutron diffraction Rietveld analysis. These oxides crystallize in a tetragonal structure in the P4/m space group with Ni3+ or Co3+ partially occupying 6-coordinated (1a) and 5-coordinated (4j) sites of the La4BaCu5O13+&#948; 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 La4BaCu5O13+&#948;