Crystal Structure of the High Tc Superconductor TmBa2Cu3O7-δ

Abstract
The crystal structure of the high T c superconductor TmBa2Cu3O7-δ has been determined by Rietveld analysis of X-ray powder diffraction data. The crystal system is orthorhombic (space group Pmmm) with lattice parameters a=3.8746(2) Å, b=3.8087(1) Å and c=11.6655(6) Å. The structure is isomorphic with YBa2Cu3O7-δ. The Tm and Ba atoms have an ordered arrangement, O in the z=1/2 plane is completely missing and O on the basal Cu plane is deficient. The compound shows superconductivity at 90.5 K (midpoint) with the transition width of 3.0 K.