Crystal Structure of the Superconductor Ba1.8Nd1.2Cu3O7-y

Abstract
The structure parameters of a superconductor with the nominal composition Ba1.8Nd1.2Cu3O7-y were refined by the Rietveld analysis of TOF neutron powder diffraction data. This material is tetragonal with lattice constants a=3.8919 Å and c=11.6811 Å and isomorphous with Ba1.5La1.5Cu3Oy with an oxygen-deficient triperovskite structure. An oxygen site at (0, 1/2, 0) is 49% occupied, the Nd3+ ion at (1/2, 1/2, 1/2) is coordinated to eight oxide ions, and a metal site at (1/2, 1/2, 0.1842) is 90% and 10% occupied by Ba2+ and Nd3+ ions, respectively.