A high-resolution neutron powder diffraction study on high-Tc superconductor YBa2Cu3O7

A high-resolution neutron time-of-flight diffraction measurement of superconductive Y-Ba-Cu-O (T_co = 91 K) has been performed both at room temperature and at 77 K. Profile refinements of the measured data resulted in a unit cell of stoichiometry YBa₂Cu₃O₇. The positions of the oxygen deficiencies were also determined. Refinement of the anisotropic thermal parameters for the oxygen atoms seem to indicate some changes in the form of the thermal ellipsoids of these atoms when cooled below T.