The structure of superconducting Pb 2Sr 2Y 1−xCa xCu 3O 8 by single crystal neutron diffraction data

Abstract

The structures of two superconducting Pb 2Sr 2Y 1−xCa xCu 3O 8 crystals have been refined by single-crystal neutron diffraction data at room temperature. They have been found to belong to space group Pman. The calcium content of the two crystals, showing superconducting transitions at 65K and 38K, were x=0.27 and x=0.37, respectively. The comparison of the interatomic distances to the ones reported previously for the undoped non-superconducting compound indicates that the charge transfer takes place from the (Y,Ca) layers to the CuO 2 layers. The apical CuO distance is not implicated in the charge transfer, contrary to what occurs in YBa 2Cu 3O 6+x