Crystal Structures of YBa₂Cu_3-δA_δO_9-γ (A=Ni, Zn and Co)

Abstract

A structural study of orthorhombic YBa 2 Cu 3 O 6.94 , YBa 2 Cu 2.8 Ni 0.2 O 6.85 and YBa 2 Cu 2.7 Zn 0.3 O 6.75 , and tetragonal YBa 2 Cu 2 CoO 7.16 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 Cu 2 site 2q(00 z ) with z =0.36. The zinc atoms occupy the Cu 1 site 1a(000) and the Cu 2 site with occupancies of 0.20(5) and 0.05(2). In the tetragonal YBa 2 Cu 2 CoO 7.16 , cobalt atoms were found at both the Cu 1 and Cu 2 sites with occupancies of 0.83(2) and 0.08(1).