Crystal Structure of Ba2HoCu3O7-x Determined by Neutron Powder Diffraction

Abstract
The crystal structure of the high T c superconductor Ba2HoCu3O7-x has been determined by Rietveld analysis of TOF neutron powder diffraction data. This compound is orthorhombic (space group: Pmmm) with lattice parameters a = 3.8851 Å, b = 3.8205 Å and c = 11.6822 Å. It is isomorphic with Ba2YCu3O7-x . Ba and Ho atoms are ordered in a sequence of Ba-Ho-Ba along the c-axis, oxygen atoms on a z = 1/2 plane are missing, and an oxygen site at (1/2, 0, 0) is selectively occupied. The chemical composition of the present sample has been determined to be Ba2HoCu3O6.96.