Neutron structural studies of the superconducting YBa2(Cu1-xVx)3O7-δ system at x=0.04 and 0.06

We have investigated the influence of the incorporation of V ions with Cu ions on the structural features of the YBa2Cu3O7-δ superconductor by Rietveld refinement of neutron diffraction patterns of two YBa2(Cu1-xVx)3O7-δ samples with (sample A) x=0.04 and (sample B) x=0.05. Neutron data confirm an orthorhombic structure with space group Pmmm for both samples, and the lattice parameters are in excellent agreement with those obtained from X-ray diffraction. The oxygen contents per formula unit of these samples are in good agreement with the iodometrically obtained values. V ions occupy Cu(1) and Cu(2) sites in equal proportions in the mixed valence state (4+, 5+) without affecting the orthorhombic structure and Tc of the compound. A correlation exists between the Cu(1)-O(2) bond length and the measured Tc values of both samples. (author)