Crystal Structures of YBa2Cu3-δAδO9-γ (A=Ni, Zn and Co)

A structural study of orthorhombic YBa2Cu3O6.94, YBa2Cu2.8Ni0.2O6.85 and YBa2Cu2.7Zn0.3O6.75, and tetragonal YBa2Cu2CoO7.16 by means of X-ray and time-of-flight type (TOF) neutron diffractometers was carried out to determine the locations of the dopant atoms, Ni, Zn and Co, in the 1-2-3 (Y/Ba/Cu) oxide. The nickel atoms occupy only the Cu2 site 2q(00z) with z=0.36. The zinc atoms occupy the Cu1 site 1a(000) and the Cu2 site with occupancies of 0.20(5) and 0.05(2). In the tetragonal YBa2Cu2CoO7.16, cobalt atoms were found at both the Cu1 and Cu2 sites with occupancies of 0.83(2) and 0.08(1).