Neutron-diffraction study of NdBa2Cu3O/sub 7+//sub x/ with x = 0.06 and 0.18

Two samples of NdBa2Cu3O/sub 7+//sub x/ with zero-resistance transition temperatures of 85 K (x = 0.06) and 90 K (x = 0.18), respectively, were studied by using neutron-diffraction powder profile analysis. The compounds crystallize in the same orthorhombic, oxygen-deficient perovskite structure with space group Pmmm, in which both 1e(0,(1/2,0) and 1b((1/2,0,0) sites are occupied partially by oxygen atoms, with a majority of atoms being located in the 1e sites. The final refinements converge to weighted profile R factors, R/sub wp/, of 7.05% and 7.58% for the 90- and 85-K samples, respectively. The significant differences between the two samples are the oxygen content and the regular changes of all the Cu-O bond distances in the structures